diff --git a/docs/conf.py b/docs/conf.py
index 6c389f551..c8abd31a7 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -54,9 +54,7 @@ extensions = [
     'sphinx_markdown_tables'
 ]  # yapf: disable
 
-autodoc_mock_imports = [
-    'cv2', 'mmcv._ext', 'mmcv.utils.ext_loader', 'torchvision'
-]
+autodoc_mock_imports = ['mmcv._ext', 'mmcv.utils.ext_loader', 'torchvision']
 autosectionlabel_prefix_document = True
 
 # Add any paths that contain templates here, relative to this directory.
diff --git a/requirements/docs.txt b/requirements/docs.txt
index e14f32b69..f5a015902 100644
--- a/requirements/docs.txt
+++ b/requirements/docs.txt
@@ -1,3 +1,4 @@
 m2r
+opencv-python
 sphinx_markdown_tables
 torch