diff --git a/deepmd/utils/convert.py b/deepmd/utils/convert.py
index 6fbc9a36ac..ef5663f75a 100644
--- a/deepmd/utils/convert.py
+++ b/deepmd/utils/convert.py
@@ -4,25 +4,6 @@
 from google.protobuf import text_format
 
 
-def convert_13_to_21(input_model: str, output_model: str):
-    """Convert DP 1.3 graph to 2.1 graph.
-    
-    Parameters
-    ----------
-    input_model : str
-        filename of the input graph
-    output_model : str
-        filename of the output graph
-    """
-    convert_pb_to_pbtxt(input_model, 'frozen_model.pbtxt')
-    convert_dp13_to_dp20('frozen_model.pbtxt')
-    convert_dp20_to_dp21('frozen_model.pbtxt')
-    convert_pbtxt_to_pb('frozen_model.pbtxt', output_model)
-    if os.path.isfile('frozen_model.pbtxt'):
-        os.remove('frozen_model.pbtxt')
-    print("the converted output model (2.1 support) is saved in %s" % output_model)
-
-
 def convert_13_to_21(input_model: str, output_model: str):
     """Convert DP 1.3 graph to 2.1 graph.