diff --git a/python/setup.py.server.in b/python/setup.py.server.in
index 4c726aa3a760bbdf66212685e72ab818bb9180f5..2ab92745d0af1981e0e38fd90a3268fb04df4b90 100644
--- a/python/setup.py.server.in
+++ b/python/setup.py.server.in
@@ -30,7 +30,7 @@ max_version, mid_version, min_version = python_version()
 
 REQUIRED_PACKAGES = [
     'six >= 1.10.0', 'protobuf >= 3.1.0','paddlepaddle',
-    'paddle_serving_client'
+    'paddle_serving_client', flask >= 1.1.1
 ]
 
 packages=['paddle_serving_server',