diff --git a/src/collapse/collapse.jsx b/src/collapse/collapse.jsx
index 8bcdae9dc8..e62682744c 100644
--- a/src/collapse/collapse.jsx
+++ b/src/collapse/collapse.jsx
@@ -89,10 +89,11 @@ class Collapse extends React.Component {
     onItemClick(key) {
         let expandedKeys = this.state.expandedKeys;
         if (this.props.accordion) {
-            expandedKeys = expandedKeys[0] === key ? [] : [key];
+            expandedKeys = String(expandedKeys[0]) === String(key) ? [] : [key];
         } else {
             expandedKeys = [...expandedKeys];
-            const index = expandedKeys.indexOf(key);
+            const stringKey = String(key);
+            const index = expandedKeys.findIndex(k => String(k) === stringKey);
             const isExpanded = index > -1;
             if (isExpanded) {
                 expandedKeys.splice(index, 1);
@@ -127,7 +128,7 @@ class Collapse extends React.Component {
         let isExpanded = false;
 
         if (this.props.accordion) {
-            isExpanded = expandedKeys[0] === key;
+            isExpanded = String(expandedKeys[0]) === String(key);
         } else {
             isExpanded = expandedKeys.some(expandedKey => {
                 if (
diff --git a/test/collapse/index-spec.js b/test/collapse/index-spec.js
index 72ec5937f6..13a30b56b3 100644
--- a/test/collapse/index-spec.js
+++ b/test/collapse/index-spec.js
@@ -9,6 +9,9 @@ Enzyme.configure({ adapter: new Adapter() });
 
 const Panel = Collapse.Panel;
 
+/* global describe, it */
+/* eslint-disable react/jsx-filename-extension */
+
 describe('Collapse', () => {
     describe('render', () => {
         it('[normal] Should render from children', () => {
@@ -39,8 +42,256 @@ describe('Collapse', () => {
             const wrapper = mount(<Collapse dataSource={list} />);
             assert(wrapper.find(Panel).length === 2);
         });
+
+        it('should default expand keys passed in `defaultExpandedKeys`', () => {
+            const wrapper = mount(
+                <Collapse defaultExpandedKeys={[]}>
+                    <Panel title="Pannel Title">Pannel Content</Panel>
+                    <Panel title="Pannel Title">Pannel Content</Panel>
+                    <div>others</div>
+                </Collapse>
+            );
+            assert(wrapper.find(Collapse).length === 1);
+            assert(wrapper.find(Panel).length === 2);
+        });
     });
 
+    describe('defaultExpandedKeys', () => {
+        describe('default mode', () => {
+            it('should expand panel with string key', () => {
+                const wrapper = mount(
+                    <Collapse defaultExpandedKeys={["2"]}>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        
+                        <div>others</div>
+                    </Collapse>
+                );
+                const el = wrapper
+                    .find('.next-collapse-panel')
+                    .at(2);
+                assert(el.hasClass('next-collapse-panel-expanded'));
+            });
+    
+            it('should expand panel with number key', () => {
+                const wrapper = mount(
+                    <Collapse defaultExpandedKeys={[2]}>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        
+                        <div>others</div>
+                    </Collapse>
+                );
+                const el = wrapper
+                    .find('.next-collapse-panel')
+                    .at(2);
+                assert(el.hasClass('next-collapse-panel-expanded'));
+            });
+    
+            it('should close default expanded string keys', () => {
+                const wrapper = mount(
+                    <Collapse defaultExpandedKeys={["2"]}>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        
+                        <div>others</div>
+                    </Collapse>
+                );
+                wrapper
+                    .find('.next-collapse-panel-title')
+                    .at(2)
+                    .simulate('click');
+                assert(wrapper.find('.next-collapse-panel-expanded').length === 0);
+            });
+    
+            it('should close default expanded number keys', () => {
+                const wrapper = mount(
+                    <Collapse defaultExpandedKeys={[2]}>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        
+                        <div>others</div>
+                    </Collapse>
+                );
+                wrapper
+                    .find('.next-collapse-panel-title')
+                    .at(2)
+                    .simulate('click');
+                assert(wrapper.find('.next-collapse-panel-expanded').length === 0);
+            });
+    
+            it('should open default expanded datasource using number keys', () => {
+                const list = [
+                    {
+                        title: 'Well, hello there',
+                        key: 0,
+                        content:
+                            'Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.',
+                    },
+                    {
+                        title: 'Well, hello there',
+                        key: 1,
+                        content:
+                            'Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.',
+                    },
+                ];
+                const wrapper = mount(<Collapse dataSource={list} defaultExpandedKeys={[1]} />);
+                const el = wrapper
+                    .find('.next-collapse-panel')
+                    .at(1);
+                assert(el.hasClass('next-collapse-panel-expanded'));
+            });
+    
+            it('should close default expanded datasource using number keys on click', () => {
+                const list = [
+                    {
+                        title: 'Well, hello there',
+                        key: 0,
+                        content:
+                            'Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.',
+                    },
+                    {
+                        title: 'Well, hello there',
+                        key: 1,
+                        content:
+                            'Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.',
+                    },
+                ];
+                const wrapper = mount(<Collapse dataSource={list} defaultExpandedKeys={[1]} />);
+                wrapper
+                    .find('.next-collapse-panel-title')
+                    .at(1)
+                    .simulate('click');
+                assert(wrapper.find('.next-collapse-panel-expanded').length === 0);
+            });
+        })
+
+        describe('accordian mode', () => {
+            it('should expand panel with string key', () => {
+                const wrapper = mount(
+                    <Collapse defaultExpandedKeys={["2"]} accordion>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        
+                        <div>others</div>
+                    </Collapse>
+                );
+                const el = wrapper
+                    .find('.next-collapse-panel')
+                    .at(2);
+                assert(el.hasClass('next-collapse-panel-expanded'));
+            });
+    
+            it('should expand panel with number key', () => {
+                const wrapper = mount(
+                    <Collapse defaultExpandedKeys={[2]} accordion>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        
+                        <div>others</div>
+                    </Collapse>
+                );
+                const el = wrapper
+                    .find('.next-collapse-panel')
+                    .at(2);
+                assert(el.hasClass('next-collapse-panel-expanded'));
+            });
+    
+            it('should close default expanded string keys', () => {
+                const wrapper = mount(
+                    <Collapse defaultExpandedKeys={["2"]} accordion>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        
+                        <div>others</div>
+                    </Collapse>
+                );
+                wrapper
+                    .find('.next-collapse-panel-title')
+                    .at(2)
+                    .simulate('click');
+                assert(wrapper.find('.next-collapse-panel-expanded').length === 0);
+            });
+    
+            it('should close default expanded number keys', () => {
+                const wrapper = mount(
+                    <Collapse defaultExpandedKeys={[2]} accordion>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        <Panel title="Pannel Title">Pannel Content</Panel>
+                        
+                        <div>others</div>
+                    </Collapse>
+                );
+                wrapper
+                    .find('.next-collapse-panel-title')
+                    .at(2)
+                    .simulate('click');
+                assert(wrapper.find('.next-collapse-panel-expanded').length === 0);
+            });
+    
+            it('should open default expanded datasource using number keys', () => {
+                const list = [
+                    {
+                        title: 'Well, hello there',
+                        key: 0,
+                        content:
+                            'Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.',
+                    },
+                    {
+                        title: 'Well, hello there',
+                        key: 1,
+                        content:
+                            'Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.',
+                    },
+                ];
+                const wrapper = mount(<Collapse dataSource={list} defaultExpandedKeys={[1]}  accordion/>);
+                const el = wrapper
+                    .find('.next-collapse-panel')
+                    .at(1);
+                assert(el.hasClass('next-collapse-panel-expanded'));
+            });
+    
+            it('should close default expanded datasource using number keys on click', () => {
+                const list = [
+                    {
+                        title: 'Well, hello there',
+                        key: 0,
+                        content:
+                            'Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.',
+                    },
+                    {
+                        title: 'Well, hello there',
+                        key: 1,
+                        content:
+                            'Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.',
+                    },
+                ];
+                const wrapper = mount(<Collapse dataSource={list} defaultExpandedKeys={[1]}  accordion/>);
+                wrapper
+                    .find('.next-collapse-panel-title')
+                    .at(1)
+                    .simulate('click');
+                assert(wrapper.find('.next-collapse-panel-expanded').length === 0);
+            });
+        })
+    })
+
     describe('event', () => {
         it('Should expanded by click', () => {
             const collapse = (