diff --git a/excel_reader.py b/excel_reader.py
index ad75e5b..dbc19f7 100755
--- a/excel_reader.py
+++ b/excel_reader.py
@@ -12,7 +12,7 @@ chinnese_number_prefix = ['13', '15', '18']
 
 def read_contacts(file_name) -> list:
     print("read file " + file_name)
-    contact_list_in_json = pandas.read_excel(file_name).to_json(orient='records')
+    contact_list_in_json = pandas.read_excel(file_name, dtype={'passport': str}).to_json(orient='records')
     contact_dict_list = json.loads(contact_list_in_json)
     contact_list = []
     for contact_dict in contact_dict_list: