diff --git a/imperative/python/scripts/format.sh b/imperative/python/scripts/format.sh
index 827b96c3d73b7527a3b8d37cbc7a822d860a2679..582cc74a0bacdc9ab3caeff9a71c6b8b7847bb18 100755
--- a/imperative/python/scripts/format.sh
+++ b/imperative/python/scripts/format.sh
@@ -31,4 +31,4 @@ fi
 # do not isort megengine/__init__.py file, caused we must
 # init library load path before load dependent lib in core
 isort $ISORT_ARG -j $(nproc) -rc "${directories[@]}" -s megengine/__init__.py
-black $BLACK_ARG --target-version=py35 -- "${directories[@]}"
+black $BLACK_ARG --target-version=py35 --exclude='_imperative_rt/.*\.pyi$' -- "${directories[@]}"