diff --git a/dpdata/rdkit/utils.py b/dpdata/rdkit/utils.py
index a8a52be86..0dc0a9a31 100644
--- a/dpdata/rdkit/utils.py
+++ b/dpdata/rdkit/utils.py
@@ -1,5 +1,8 @@
-from rdkit import Chem
-from rdkit.Chem import AllChem
+try:
+    from rdkit import Chem
+    from rdkit.Chem import AllChem
+except ModuleNotFoundError:
+    pass
 import numpy as np
 
 def mol_to_system_data(mol):
@@ -105,4 +108,4 @@ def combine_molecules(mols):
                 mols[0].AddConformer(conf, assignId=True)
         return mols[0]
     else:
-        raise ValueError("molecules are not of the same topology.")
\ No newline at end of file
+        raise ValueError("molecules are not of the same topology.")