diff --git a/csst_proto/config.py b/csst_proto/config.py
index 1180e5fd8f0afca1effecec0023ac20a6a17d61a..d32fcd4983db880ba57e12756a1a3cad735decfd 100644
--- a/csst_proto/config.py
+++ b/csst_proto/config.py
@@ -24,7 +24,7 @@ HERE: str = os.path.dirname(__file__)
 # 这个函数演示了如何利用随包数据
 # 当config_path被指定时，会读取指定的config_path
 # 当config_path=None时，读取随包数据中的config/default_config.toml
-def read_config(config_path: Optional[str] = None):
+def read_config(config_path: Optional[str] = None) -> dict:
     """
     Get config info from a toml file.
 
diff --git a/csst_proto/demo.py b/csst_proto/demo.py
index 89d5cb0f6d30492d2cf05bbb98231a6f1032d1cf..f75f4ecb040005366ac347fddcf383c54285f609 100644
--- a/csst_proto/demo.py
+++ b/csst_proto/demo.py
@@ -11,7 +11,7 @@ Modified-History:
 from typing import Any
 
 
-def demo_function(*args: Any):
+def demo_function(*args: Any) -> int:
     """
     A demo function.
 
@@ -66,9 +66,9 @@ class DemoClass:
     >>> a.say_hello()
     """
 
-    def __init__(self, first_name, last_name):
+    def __init__(self, first_name, last_name) -> None:
         self.first_name = first_name
         self.last_name = last_name
 
-    def say_hello(self):
+    def say_hello(self) -> None:
         print("Hello, {} {}!".format(self.first_name, self.last_name))
diff --git a/csst_proto/flip_image.py b/csst_proto/flip_image.py
index a95d4a364429bc3bbff00ea97f6e114de66e3aa4..9b462462c0f8266aa70142052e9333395581fb23 100644
--- a/csst_proto/flip_image.py
+++ b/csst_proto/flip_image.py
@@ -61,7 +61,7 @@ def flip_image(image: np.ndarray, use_numpy: bool = False) -> np.ndarray:
 
 
 # 此函数读取了随包数据中的test_image.txt
-def read_default_image():
+def read_default_image() -> np.ndarray:
     """
     Read default image.
 
diff --git a/csst_proto/flip_image_in_parallel.py b/csst_proto/flip_image_in_parallel.py
index dc35acb913bf654cfe11065e2394d2c9d15f203d..8f78572950b5fab9c4a99dd1e8ba81165952c057 100644
--- a/csst_proto/flip_image_in_parallel.py
+++ b/csst_proto/flip_image_in_parallel.py
@@ -30,7 +30,8 @@ def flip_multiple_images_mp(images: list[np.ndarray], n_jobs: int) -> list[np.nd
 
     Returns
     -------
-    The flipped image list.
+    list[np.ndarray]
+        The flipped image list.
     """
     with multiprocessing.Pool(n_jobs) as p:
         results = p.map(flip_image, images)
@@ -52,7 +53,8 @@ def flip_multiple_images_jl(images: list[np.ndarray], n_jobs: int) -> list[np.nd
 
     Returns
     -------
-    The flipped image list.
+    list[np.ndarray]
+        The flipped image list.
     """
     return joblib.Parallel(n_jobs=n_jobs, backend="multiprocessing")(
         joblib.delayed(flip_image)(image) for image in images