diff --git a/python/paddle_serving_client/client.py b/python/paddle_serving_client/client.py
index 0c5aa23c183990bc248053c43a430cba2d2008a2..80d62826c4a5db842572e3144047fdd42bb06d23 100755
--- a/python/paddle_serving_client/client.py
+++ b/python/paddle_serving_client/client.py
@@ -307,6 +307,7 @@ class Client(object):
         if isinstance(feed, dict):
             feed_batch.append(feed)
         elif isinstance(feed, list):
+            # batch_size must be 1, cause batch is already in Tensor.
             if len(feed) != 1:
                 raise ValueError("Feed only list = [dict]")
             feed_batch = feed
@@ -328,7 +329,8 @@ class Client(object):
 
         fetch_names = []
         counter = 0
-        batch_size = len(feed_batch)  # batch_size must be 1.
+        # batch_size must be 1, cause batch is already in Tensor.
+        batch_size = len(feed_batch)
 
         for key in fetch_list:
             if key in self.fetch_names_: