diff --git a/docs/conf.py b/docs/conf.py
index e709591e..8a212ca4 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -38,7 +38,9 @@ extensions = [
     'sphinx_markdown_tables',
 ]
 
-autodoc_mock_imports = ['torch', 'torchvision', 'mmcv', 'mmocr.version']
+autodoc_mock_imports = [
+    'torch', 'torchvision', 'mmcv', 'mmocr.version', 'mmdet'
+]
 
 # Add any paths that contain templates here, relative to this directory.
 templates_path = ['_templates']
diff --git a/requirements/docs.txt b/requirements/docs.txt
index be041dcc..89fbf86c 100644
--- a/requirements/docs.txt
+++ b/requirements/docs.txt
@@ -1,4 +1,3 @@
-numpy
 recommonmark
 sphinx
 sphinx_markdown_tables
diff --git a/requirements/readthedocs.txt b/requirements/readthedocs.txt
index 5ac0dc44..fad43ef7 100644
--- a/requirements/readthedocs.txt
+++ b/requirements/readthedocs.txt
@@ -3,8 +3,6 @@ kwarray
 lmdb
 matplotlib
 mmcv
-mmdet==2.9.0
-numpy
 Polygon3
 pyclipper
 rapidfuzz