diff --git a/src/main.rs b/src/main.rs
index 88a16a5..f822d30 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,7 +1,5 @@
+mod util;
 mod v4;
-mod map_util;
-mod common_util;
-mod sign_algorithm;
 
 fn main() {
     println!("Hello, world!");
diff --git a/src/common_util.rs b/src/util/common_util.rs
similarity index 100%
rename from src/common_util.rs
rename to src/util/common_util.rs
diff --git a/src/map_util.rs b/src/util/map_util.rs
similarity index 100%
rename from src/map_util.rs
rename to src/util/map_util.rs
diff --git a/src/util/mod.rs b/src/util/mod.rs
new file mode 100644
index 0000000..f3c5bd9
--- /dev/null
+++ b/src/util/mod.rs
@@ -0,0 +1,3 @@
+pub(crate) mod common_util;
+pub(crate) mod map_util;
+pub(crate) mod sign_algorithm;
\ No newline at end of file
diff --git a/src/sign_algorithm.rs b/src/util/sign_algorithm.rs
similarity index 100%
rename from src/sign_algorithm.rs
rename to src/util/sign_algorithm.rs
diff --git a/src/v4/aliyun_util.rs b/src/v4/aliyun_util.rs
index 9dc339c..4bce013 100644
--- a/src/v4/aliyun_util.rs
+++ b/src/v4/aliyun_util.rs
@@ -4,9 +4,9 @@ use std::time::SystemTime;
 
 use rand::random;
 
-use crate::common_util::{join_slices, percent_encode};
-use crate::map_util::BTreeMapAddKv;
-use crate::sign_algorithm::SignAlgorithm;
+use crate::util::common_util::{join_slices, percent_encode};
+use crate::util::map_util::BTreeMapAddKv;
+use crate::util::sign_algorithm::SignAlgorithm;
 use crate::v4::access_key::{AccessKey, DerivedAccessKey};
 use crate::v4::constant::{ALIYUN_V4, ALIYUN_V4_REQUEST, CONTENT_TYPE_APPLICATION_JSON, HEADER_ACCEPT, HEADER_AUTHORIZATION, HEADER_CONTENT_TYPE, HEADER_HOST, HEADER_USER_AGENT, HEADER_X_ACS_PREFIX, HEADER_X_ASC_ACCESS_KEY_ID, HEADER_X_ASC_ACTION, HEADER_X_ASC_CONTENT_SHA256, HEADER_X_ASC_CONTENT_SM3, HEADER_X_ASC_DATE, HEADER_X_ASC_SECURITY_TOKEN, HEADER_X_ASC_SIGNATURE_NONCE, HEADER_X_ASC_VERSION, REGION_CENTER};