diff --git a/dragonfly-client/src/proxy/header.rs b/dragonfly-client/src/proxy/header.rs
index e56b9885..11898023 100644
--- a/dragonfly-client/src/proxy/header.rs
+++ b/dragonfly-client/src/proxy/header.rs
@@ -79,11 +79,15 @@ pub const DRAGONFLY_PIECE_LENGTH_HEADER: &str = "X-Dragonfly-Piece-Length";
 pub const DRAGONFLY_CONTENT_FOR_CALCULATING_TASK_ID_HEADER: &str =
     "X-Dragonfly-Content-For-Calculating-Task-ID";
 
-/// DRAGONFLY_TASK_DOWNLOAD_FINISHED_HEADER is the header key to indicate whether the task download finished.
+/// DRAGONFLY_TASK_DOWNLOAD_FINISHED_HEADER is the response header key to indicate whether the task download finished.
 /// When the task download is finished, the response will include this header with the value `"true"`,
 /// indicating that the download hit the local cache.
 pub const DRAGONFLY_TASK_DOWNLOAD_FINISHED_HEADER: &str = "X-Dragonfly-Task-Download-Finished";
 
+/// DRAGONFLY_TASK_ID_HEADER is the response header key of task id. Client will calculate the task ID
+/// based on `url`, `piece_length`, `tag`, `application`, and `filtered_query_params`.
+pub const DRAGONFLY_TASK_ID_HEADER: &str = "X-Dragonfly-Task-ID";
+
 /// get_tag gets the tag from http header.
 pub fn get_tag(header: &HeaderMap) -> Option<String> {
     header
diff --git a/dragonfly-client/src/proxy/mod.rs b/dragonfly-client/src/proxy/mod.rs
index 2df3170b..04e56b3e 100644
--- a/dragonfly-client/src/proxy/mod.rs
+++ b/dragonfly-client/src/proxy/mod.rs
@@ -768,7 +768,10 @@ async fn proxy_via_dfdaemon(
 
     // Construct the response.
     let mut response = Response::new(boxed_body);
-    *response.headers_mut() = make_response_headers(download_task_started_response.clone())?;
+    *response.headers_mut() = make_response_headers(
+        message.task_id.as_str(),
+        download_task_started_response.clone(),
+    )?;
     *response.status_mut() = http::StatusCode::OK;
 
     // Return the response if the client return the first piece.
@@ -1151,6 +1154,7 @@ fn make_download_url(
 
 /// make_response_headers makes the response headers.
 fn make_response_headers(
+    task_id: &str,
     mut download_task_started_response: DownloadTaskStartedResponse,
 ) -> ClientResult<hyper::header::HeaderMap> {
     // Insert the content range header to the response header.
@@ -1178,6 +1182,11 @@ fn make_response_headers(
         );
     }
 
+    download_task_started_response.response_header.insert(
+        header::DRAGONFLY_TASK_ID_HEADER.to_string(),
+        task_id.to_string(),
+    );
+
     hashmap_to_headermap(&download_task_started_response.response_header)
 }