diff --git a/hack/util.sh b/hack/util.sh
index 86591481b..3ea65309a 100755
--- a/hack/util.sh
+++ b/hack/util.sh
@@ -669,7 +669,8 @@ function util::set_mirror_registry_for_china_mainland() {
     "cluster/images/buildx.Dockerfile"
   )
   for dockerfile in "${dockerfile_list[@]}"; do
-    grep 'mirrors.ustc.edu.cn' ${repo_root}/${dockerfile} > /dev/null || sed -i'' -e "s#FROM alpine:3.15.1#FROM alpine:3.15.1\nRUN echo -e http://mirrors.ustc.edu.cn/alpine/v3.15/main/ > /etc/apk/repositories#" ${repo_root}/${dockerfile}
+    grep 'mirrors.ustc.edu.cn' ${repo_root}/${dockerfile} > /dev/null || sed -i '' -e "1a\\
+RUN echo -e http://mirrors.ustc.edu.cn/alpine/v3.15/main/ > /etc/apk/repositories" ${repo_root}/${dockerfile}
   done
 }