diff --git a/tools/infer/py_infer.py b/tools/infer/py_infer.py
index b566092bc1fa069e6ffd4b051a5de78701dad9ea..8236bc6f96d0c547d0ef685315df1ce5af58c628 100644
--- a/tools/infer/py_infer.py
+++ b/tools/infer/py_infer.py
@@ -87,6 +87,7 @@ def main():
     exe, program, feed_names, fetch_lists = create_predictor(args)
 
     data = preprocess(args.image_file, operators)
+    data = np.expand_dims(data, axis=0)
     outputs = exe.run(program,
                       feed={feed_names[0]: data},
                       fetch_list=fetch_lists,