diff --git a/biz/ffmpeg.py b/biz/ffmpeg.py
index 426c996..3d2f6e3 100644
--- a/biz/ffmpeg.py
+++ b/biz/ffmpeg.py
@@ -22,6 +22,7 @@ def parse_ffmpeg_task(task_info, template_info):
         task_params_str = task_info.get("taskParams", "{}")
         span.set_attribute("task_params", task_params_str)
         task_params = json.loads(task_params_str)
+        task_params_orig = json.loads(task_params_str)
         for part in template_info.get("video_parts"):
             source = parse_video(part.get('source'), task_params, template_info)
             if not source:
@@ -29,7 +30,7 @@ def parse_ffmpeg_task(task_info, template_info):
                 continue
             only_if = part.get('only_if', '')
             if only_if:
-                if not check_placeholder_exist(only_if, task_params):
+                if not check_placeholder_exist(only_if, task_params_orig):
                     logger.info("because only_if exist, placeholder: %s not exist, skip part: %s", only_if, part)
                     continue
             sub_ffmpeg_task = FfmpegTask(source)