diff --git a/examples/transformer_tts/synthesis.py b/examples/transformer_tts/synthesis.py
index effbffdc7a0cc21793a72eecd3ba39ead469ecce..422eb6c8cd15b316b2da2934f016d24f306e9146 100644
--- a/examples/transformer_tts/synthesis.py
+++ b/examples/transformer_tts/synthesis.py
@@ -44,7 +44,8 @@ def add_config_options_to_parser(parser):
         "--max_len",
         type=int,
         default=1000,
-        help="The max length of audio when synthsis.")
+        help="The max length of spectrum when synthesize. If the length of synthetical spectrum is lager than max_len, spectrum will be cut off."
+    )
 
     parser.add_argument(
         "--checkpoint_transformer",