diff --git a/API_Reference.py b/API_Reference.py
index 207bd25..41bd882 100644
--- a/API_Reference.py
+++ b/API_Reference.py
@@ -343,6 +343,8 @@ guan.write_file_list_in_markdown(directory='./', filename='a', reverse_positive_
 
 repeated_file = guan.find_repeated_file_with_same_filename(directory='./', missed_directory='./missed_directory', num=1000)
 
+guan.count_file_in_sub_directory(directory='./', smaller_than_num=None)
+
 guan.creat_necessary_file(directory, filename='readme', file_format='.md', content='', overwrite=None)
 
 guan.delete_file_with_specific_name(directory, filename='readme', file_format='.md')
diff --git a/PyPI/setup.cfg b/PyPI/setup.cfg
index 5e29fd0..24f12ea 100644
--- a/PyPI/setup.cfg
+++ b/PyPI/setup.cfg
@@ -1,7 +1,7 @@
 [metadata]
 # replace with your username:
 name = guan
-version = 0.0.139
+version = 0.0.140
 author = guanjihuan
 author_email = guanjihuan@163.com
 description = An open source python package
diff --git a/PyPI/src/guan.egg-info/PKG-INFO b/PyPI/src/guan.egg-info/PKG-INFO
index dddd3b9..b5ec5cb 100644
--- a/PyPI/src/guan.egg-info/PKG-INFO
+++ b/PyPI/src/guan.egg-info/PKG-INFO
@@ -1,6 +1,6 @@
 Metadata-Version: 2.1
 Name: guan
-Version: 0.0.139
+Version: 0.0.140
 Summary: An open source python package
 Home-page: https://py.guanjihuan.com
 Author: guanjihuan
diff --git a/PyPI/src/guan/__init__.py b/PyPI/src/guan/__init__.py
index ef25d2a..a191565 100644
--- a/PyPI/src/guan/__init__.py
+++ b/PyPI/src/guan/__init__.py
@@ -2,7 +2,7 @@
 
 # With this package, you can calculate band structures, density of states, quantum transport and topological invariant of tight-binding models by invoking the functions you need. Other frequently used functions are also integrated in this package, such as file reading/writing, figure plotting, data processing.
 
-# The current version is guan-0.0.139, updated on September 23, 2022.
+# The current version is guan-0.0.140, updated on September 30, 2022.
 
 # Installation: pip install --upgrade guan
 
@@ -2680,6 +2680,30 @@ def find_repeated_file_with_same_filename(directory='./', missed_directory='./mi
             repeated_file.append(item)
     return repeated_file
 
+def count_file_in_sub_directory(directory='./', smaller_than_num=None):
+    import os
+    from collections import Counter
+    dirs_list = []
+    for root, dirs, files in os.walk(directory):
+        if dirs != []:
+            for i0 in range(len(dirs)):
+                dirs_list.append(root+'/'+dirs[i0])
+    for sub_dir in dirs_list:
+        file_list = []
+        for root, dirs, files in os.walk(sub_dir):
+            for i0 in range(len(files)):
+                file_list.append(files[i0])
+        count_file = len(file_list)
+        if smaller_than_num == None:
+            print(sub_dir)
+            print(count_file)
+            print()
+        else:
+            if count_file<smaller_than_num:
+                print(sub_dir)
+                print(count_file)
+                print()
+
 def creat_necessary_file(directory, filename='readme', file_format='.md', content='', overwrite=None):
     import os
     directory_with_file = []