diff --git a/reallife_asset/rl_volcengine_client.py b/reallife_asset/rl_volcengine_client.py
index 55dda9f..1ff0c39 100644
--- a/reallife_asset/rl_volcengine_client.py
+++ b/reallife_asset/rl_volcengine_client.py
@@ -70,8 +70,8 @@ async def call_volcengine_api(vendor, operation, params, api_mapping):
     x_date = now.strftime("%Y%m%dT%H%M%SZ")
     short_x_date = x_date[:8]
 
-    # Payload
-    body = json.dumps(params, ensure_ascii=False)
+    # Payload - compact JSON (no extra spaces)
+    body = json.dumps(params, ensure_ascii=False, separators=(',', ':'))
     x_content_sha256 = _hash_sha256(body)
 
     # Query params: Action + Version