diff --git a/lib/renderer.js b/lib/renderer.js
index c659ee7..c5e3137 100644
--- a/lib/renderer.js
+++ b/lib/renderer.js
@@ -3,7 +3,6 @@
 const marked = require('marked');
 const { encodeURL, slugize, stripHTML, url_for, isExternalLink } = require('hexo-util');
 const MarkedRenderer = marked.Renderer;
-const { sep } = require('path');
 
 const anchorId = (str, transformOption) => {
   return slugize(str.trim(), {transform: transformOption});
@@ -91,14 +90,15 @@ class Renderer extends MarkedRenderer {
   image(href, title, text) {
     const { hexo, options } = this;
     const { relative_link } = hexo.config;
-    const { lazyload, prependRoot, postId } = options;
+    const { lazyload, prependRoot, postPath } = options;
 
     if (!/^(#|\/\/|http(s)?:)/.test(href) && !relative_link && prependRoot) {
-      if (!/^(\/|\\)/.test(href) && postId) {
+      if (!href.startsWith('/') && !href.startsWith('\\') && postPath) {
         const PostAsset = hexo.model('PostAsset');
-        // slug requires platform-specific path
-        const asset = PostAsset.findOne({ post: postId, slug: href.replace(/\/|\\/g, sep) });
-        if (asset) href = encodeURL(('/' + asset.path).replace(/\\/g, '/').replace(/\/{2,}/g, '/'));
+        // findById requires forward slash
+        const asset = PostAsset.findById(postPath + href.replace(/\\/g, '/'));
+        // asset.path is backward slash in Windows
+        if (asset) href = asset.path.replace(/\\/g, '/');
       }
       href = url_for.call(hexo, href);
     }
@@ -118,7 +118,7 @@ marked.setOptions({
 });
 
 module.exports = function(data, options) {
-  const { post_asset_folder, marked: markedCfg } = this.config;
+  const { post_asset_folder, marked: markedCfg, source_dir } = this.config;
   const { prependRoot, postAsset } = markedCfg;
   const { path, text } = data;
 
@@ -126,16 +126,16 @@ module.exports = function(data, options) {
   const renderer = new Renderer(this);
   this.execFilterSync('marked:renderer', renderer, {context: this});
 
-  let postId = '';
+  let postPath = '';
   if (path && post_asset_folder && prependRoot && postAsset) {
     const Post = this.model('Post');
     // Windows compatibility, Post.findOne() requires forward slash
-    const source = path.replace(this.source_dir, '').replace('\\', '/');
+    const source = path.substring(this.source_dir.length).replace(/\\/g, '/');
     const post = Post.findOne({ source });
-    postId = post ? post._id : '';
+    postPath = post ? source_dir + '/_posts/' + post.slug + '/' : '';
   }
 
   return marked(text, Object.assign({
     renderer
-  }, markedCfg, options, { postId }));
+  }, markedCfg, options, { postPath }));
 };