diff --git a/docs/README b/docs/README
index fe47370dc64335e6a28e822e7c8556c06aeae2c6..7fb2f1deeba9b09922537ddf9bbf0824fa602a17 100644
--- a/docs/README
+++ b/docs/README
@@ -1,7 +1,7 @@
 The documents are based on Sphinx, run the following commands to build the documents:
 
-pip install sphinx sphinx-autobuild
+pip install sphinx sphinx-autobuild sphinx-rtd-theme
 pip install recommonmark
 make html
 
-After building, the generated documents are located in _build.
\ No newline at end of file
+After building, the generated documents are located in _build.