diff --git a/demo/huge_image_demo.py b/demo/huge_image_demo.py
new file mode 100644
index 000000000..f73ab0661
--- /dev/null
+++ b/demo/huge_image_demo.py
@@ -0,0 +1,58 @@
+# Copyright (c) OpenMMLab. All rights reserved.
+from argparse import ArgumentParser
+
+from mmdet.apis import init_detector, show_result_pyplot
+
+from mmrotate.apis import inference_detector_by_patches
+
+
+def parse_args():
+    parser = ArgumentParser()
+    parser.add_argument('img', help='Image file')
+    parser.add_argument('config', help='Config file')
+    parser.add_argument('checkpoint', help='Checkpoint file')
+    parser.add_argument(
+        '--patch_sizes',
+        type=int,
+        nargs='+',
+        default=[1024],
+        help='The sizes of patches')
+    parser.add_argument(
+        '--patch_steps',
+        type=int,
+        nargs='+',
+        default=[824],
+        help='The steps between two patches')
+    parser.add_argument(
+        '--img_ratios',
+        type=float,
+        nargs='+',
+        default=[1.0],
+        help='Image resizing ratios for multi-scale detecting')
+    parser.add_argument(
+        '--merge_iou_thr',
+        type=float,
+        default=0.1,
+        help='IoU threshould for merging results')
+    parser.add_argument(
+        '--device', default='cuda:0', help='Device used for inference')
+    parser.add_argument(
+        '--score-thr', type=float, default=0.3, help='bbox score threshold')
+    args = parser.parse_args()
+    return args
+
+
+def main(args):
+    # build the model from a config file and a checkpoint file
+    model = init_detector(args.config, args.checkpoint, device=args.device)
+    # test a single image
+    result = inference_detector_by_patches(model, args.img, args.patch_sizes,
+                                           args.patch_steps, args.img_ratios,
+                                           args.merge_iou_thr)
+    # show the results
+    show_result_pyplot(model, args.img, result, score_thr=args.score_thr)
+
+
+if __name__ == '__main__':
+    args = parse_args()
+    main(args)
diff --git a/mmrotate/apis/__init__.py b/mmrotate/apis/__init__.py
index 9a53f1db2..de13731d9 100644
--- a/mmrotate/apis/__init__.py
+++ b/mmrotate/apis/__init__.py
@@ -1,4 +1,5 @@
 # Copyright (c) OpenMMLab. All rights reserved.
+from .inference import inference_detector_by_patches
 from .train import train_detector
 
-__all__ = ['train_detector']
+__all__ = ['inference_detector_by_patches', 'train_detector']
diff --git a/mmrotate/apis/inference.py b/mmrotate/apis/inference.py
new file mode 100644
index 000000000..06fc00c23
--- /dev/null
+++ b/mmrotate/apis/inference.py
@@ -0,0 +1,90 @@
+# Copyright (c) OpenMMLab. All rights reserved.
+import mmcv
+import numpy as np
+import torch
+from mmcv.ops import RoIPool
+from mmcv.parallel import collate, scatter
+from mmdet.datasets import replace_ImageToTensor
+from mmdet.datasets.pipelines import Compose
+
+from mmrotate.core import get_multiscale_patch, merge_results, slide_window
+
+
+def inference_detector_by_patches(model,
+                                  img,
+                                  sizes,
+                                  steps,
+                                  ratios,
+                                  merge_iou_thr,
+                                  bs=1):
+    """inference patches with the detector.
+
+    Split huge image(s) into patches and inference them with the detector.
+    Finally, merge patch results on one huge image by nms.
+
+    Args:
+        model (nn.Module): The loaded detector.
+        img (str | ndarray or): Either an image file or loaded image.
+        sizes (list): The sizes of patches.
+        steps (list): The steps between two patches.
+        ratios (list): Image resizing ratios for multi-scale detecting.
+        merge_iou_thr (float): IoU threshold for merging results.
+        bs (int): Batch size, must greater than or equal to 1.
+
+    Returns:
+        If imgs is a list or tuple, the same length list type results
+        will be returned, otherwise return the detection results directly.
+    """
+    assert bs >= 1, 'The batch size must greater than or equal to 1'
+    cfg = model.cfg
+    device = next(model.parameters()).device  # model device
+    cfg = cfg.copy()
+    # set loading pipeline type
+    cfg.data.test.pipeline[0].type = 'LoadPatchFromImage'
+    cfg.data.test.pipeline = replace_ImageToTensor(cfg.data.test.pipeline)
+    test_pipeline = Compose(cfg.data.test.pipeline)
+
+    if not isinstance(img, np.ndarray):
+        img = mmcv.imread(img)
+    height, width = img.shape[:2]
+    sizes, steps = get_multiscale_patch(sizes, steps, ratios)
+    windows = slide_window(width, height, sizes, steps)
+
+    # prepare patch data
+    patch_datas = []
+    for window in windows:
+        data = dict(img=img, win=window.tolist())
+        # build the data pipeline
+        data = test_pipeline(data)
+        patch_datas.append(data)
+
+    results = []
+    start = 0
+    while True:
+        data = patch_datas[start:start + bs]
+        data = collate(data, samples_per_gpu=len(data))
+        # just get the actual data from DataContainer
+        data['img_metas'] = [
+            img_metas.data[0] for img_metas in data['img_metas']
+        ]
+        data['img'] = [img.data[0] for img in data['img']]
+        if next(model.parameters()).is_cuda:
+            # scatter to specified GPU
+            data = scatter(data, [device])[0]
+        else:
+            for m in model.modules():
+                assert not isinstance(
+                    m, RoIPool
+                ), 'CPU inference with RoIPool is not supported currently.'
+
+        # forward the model
+        with torch.no_grad():
+            results.extend(model(return_loss=False, rescale=True, **data))
+
+        if start + bs >= len(patch_datas):
+            break
+        start += bs
+
+    results = merge_results(
+        results, windows[:, :2], iou_thr=merge_iou_thr, device=device)
+    return results
diff --git a/mmrotate/core/__init__.py b/mmrotate/core/__init__.py
index 1a55336e8..126eb69ea 100644
--- a/mmrotate/core/__init__.py
+++ b/mmrotate/core/__init__.py
@@ -1,5 +1,6 @@
 # Copyright (c) OpenMMLab. All rights reserved.
 from .anchor import *  # noqa: F401, F403
 from .bbox import *  # noqa: F401, F403
+from .patch import *  # noqa: F401, F403
 from .post_processing import *  # noqa: F401, F403
 from .visualization import *  # noqa: F401, F403
diff --git a/mmrotate/core/patch/__init__.py b/mmrotate/core/patch/__init__.py
new file mode 100644
index 000000000..5f112059b
--- /dev/null
+++ b/mmrotate/core/patch/__init__.py
@@ -0,0 +1,5 @@
+# Copyright (c) OpenMMLab. All rights reserved.
+from .merge_results import merge_results
+from .split import get_multiscale_patch, slide_window
+
+__all__ = ['merge_results', 'get_multiscale_patch', 'slide_window']
diff --git a/mmrotate/core/patch/merge_results.py b/mmrotate/core/patch/merge_results.py
new file mode 100644
index 000000000..5ef34c125
--- /dev/null
+++ b/mmrotate/core/patch/merge_results.py
@@ -0,0 +1,37 @@
+# Copyright (c) OpenMMLab. All rights reserved.
+import numpy as np
+import torch
+from mmcv.ops import nms_rotated
+
+
+def merge_results(results, offsets, iou_thr=0.1, device='cpu'):
+    """Merge patch results via nms.
+
+    Args:
+        results (list[np.ndarray]): A list of patches results.
+        offsets (np.ndarray): Positions of the left top points of patches.
+        iou_thr (float): The IoU threshold of NMS.
+        device (str): The device to call nms.
+
+    Retunrns:
+        list[np.ndarray]: Detection results after merging.
+    """
+    assert len(results) == offsets.shape[0], 'The `results` should has the ' \
+                                             'same length with `offsets`.'
+    merged_results = []
+    for results_pre_cls in zip(*results):
+        tran_dets = []
+        for dets, offset in zip(results_pre_cls, offsets):
+            dets[:, :2] += offset
+            tran_dets.append(dets)
+        tran_dets = np.concatenate(tran_dets, axis=0)
+
+        if tran_dets.size == 0:
+            merged_results.append(tran_dets)
+        else:
+            tran_dets = torch.from_numpy(tran_dets)
+            tran_dets = tran_dets.to(device)
+            nms_dets, _ = nms_rotated(tran_dets[:, :5], tran_dets[:, -1],
+                                      iou_thr)
+            merged_results.append(nms_dets.cpu().numpy())
+    return merged_results
diff --git a/mmrotate/core/patch/split.py b/mmrotate/core/patch/split.py
new file mode 100644
index 000000000..41b3d6457
--- /dev/null
+++ b/mmrotate/core/patch/split.py
@@ -0,0 +1,75 @@
+# Copyright (c) OpenMMLab. All rights reserved.
+from itertools import product
+from math import ceil
+
+import numpy as np
+
+
+def get_multiscale_patch(sizes, steps, ratios):
+    """Get multiscale patch sizes and steps.
+
+    Args:
+        sizes (list): A list of patch sizes.
+        steps (list): A list of steps to slide patches.
+        ratios (list): Multiscale ratios. devidie to each size and step and
+            generate patches in new scales.
+
+    Returns:
+        new_sizes (list): A list of multiscale patch sizes.
+        new_steps (list): A list of steps corresponding to new_sizes.
+    """
+    assert len(sizes) == len(steps), 'The length of `sizes` and `steps`' \
+                                     'should be the same.'
+    new_sizes, new_steps = [], []
+    size_steps = list(zip(sizes, steps))
+    for (size, step), ratio in product(size_steps, ratios):
+        new_sizes.append(int(size / ratio))
+        new_steps.append(int(step / ratio))
+    return new_sizes, new_steps
+
+
+def slide_window(width, height, sizes, steps, img_rate_thr=0.6):
+    """Slide windows in images and get window position.
+
+    Args:
+        width (int): The width of the image.
+        height (int): The height of the image.
+        sizes (list): List of window's sizes.
+        steps (list): List of window's steps.
+        img_rate_thr (float): Threshold of window area divided by image area.
+
+    Returns:
+        np.ndarray: Information of valid windows.
+    """
+    assert 1 >= img_rate_thr >= 0, 'The `in_rate_thr` should lie in 0~1'
+    windows = []
+    # Sliding windows.
+    for size, step in zip(sizes, steps):
+        assert size > step, 'Size should large than step'
+
+        x_num = 1 if width <= size else ceil((width - size) / step + 1)
+        x_start = [step * i for i in range(x_num)]
+        if len(x_start) > 1 and x_start[-1] + size > width:
+            x_start[-1] = width - size
+
+        y_num = 1 if height <= size else ceil((height - size) / step + 1)
+        y_start = [step * i for i in range(y_num)]
+        if len(y_start) > 1 and y_start[-1] + size > height:
+            y_start[-1] = height - size
+
+        start = np.array(list(product(x_start, y_start)), dtype=np.int64)
+        windows.append(np.concatenate([start, start + size], axis=1))
+    windows = np.concatenate(windows, axis=0)
+
+    # Calculate the rate of image part in each window.
+    img_in_wins = windows.copy()
+    img_in_wins[:, 0::2] = np.clip(img_in_wins[:, 0::2], 0, width)
+    img_in_wins[:, 1::2] = np.clip(img_in_wins[:, 1::2], 0, height)
+    img_areas = (img_in_wins[:, 2] - img_in_wins[:, 0]) * \
+                (img_in_wins[:, 3] - img_in_wins[:, 1])
+    win_areas = (windows[:, 2] - windows[:, 0]) * \
+                (windows[:, 3] - windows[:, 1])
+    img_rates = img_areas / win_areas
+    if not (img_rates >= img_rate_thr).any():
+        img_rates[img_rates == img_rates.max()] = 1
+    return windows[img_rates >= img_rate_thr]
diff --git a/mmrotate/datasets/pipelines/__init__.py b/mmrotate/datasets/pipelines/__init__.py
index b7f88e52d..1a90302ce 100644
--- a/mmrotate/datasets/pipelines/__init__.py
+++ b/mmrotate/datasets/pipelines/__init__.py
@@ -1,4 +1,5 @@
 # Copyright (c) OpenMMLab. All rights reserved.
+from .loading import LoadPatchFromImage
 from .transforms import PolyRandomRotate, RRandomFlip, RResize
 
-__all__ = ['RResize', 'RRandomFlip', 'PolyRandomRotate']
+__all__ = ['LoadPatchFromImage', 'RResize', 'RRandomFlip', 'PolyRandomRotate']
diff --git a/mmrotate/datasets/pipelines/loading.py b/mmrotate/datasets/pipelines/loading.py
new file mode 100644
index 000000000..dbe9f65c5
--- /dev/null
+++ b/mmrotate/datasets/pipelines/loading.py
@@ -0,0 +1,46 @@
+# Copyright (c) OpenMMLab. All rights reserved.
+import mmcv
+import numpy as np
+from mmdet.datasets.pipelines import LoadImageFromFile
+
+from ..builder import ROTATED_PIPELINES
+
+
+@ROTATED_PIPELINES.register_module()
+class LoadPatchFromImage(LoadImageFromFile):
+    """Load an patch from the huge image.
+
+    Similar with :obj:`LoadImageFromFile`, but only reserve a patch of
+    ``results['img']`` according to ``results['win']``.
+    """
+
+    def __call__(self, results):
+        """Call functions to add image meta information.
+
+        Args:
+            results (dict): Result dict with Webcam read image in
+                ``results['img']``.
+
+        Returns:
+            dict: The dict contains loaded image and meta information.
+        """
+
+        img = results['img']
+        x_start, y_start, x_stop, y_stop = results['win']
+        width = x_stop - x_start
+        height = y_stop - y_start
+
+        patch = img[y_start:y_stop, x_start:x_stop]
+        if height > patch.shape[0] or width > patch.shape[1]:
+            patch = mmcv.impad(patch, shape=(height, width))
+
+        if self.to_float32:
+            patch = patch.astype(np.float32)
+
+        results['filename'] = None
+        results['ori_filename'] = None
+        results['img'] = patch
+        results['img_shape'] = patch.shape
+        results['ori_shape'] = patch.shape
+        results['img_fields'] = ['img']
+        return results