diff --git a/zh-cn/application-dev/security/cryptoFramework-guidelines.md b/zh-cn/application-dev/security/cryptoFramework-guidelines.md
index 6083a26fd1495f1a6bbe85e617061bc9d17b0164..f3afef078d7f5c33895a4a07c06fb5ce9a74fb27 100644
--- a/zh-cn/application-dev/security/cryptoFramework-guidelines.md
+++ b/zh-cn/application-dev/security/cryptoFramework-guidelines.md
@@ -352,12 +352,11 @@ function testGenerateHmacKey() {
 import cryptoFramework from '@ohos.security.cryptoFramework';
 
 function stringToUint8Array(str: string) {
-  let arr = [];
+  let arr = new Uint8Array(str.length);
   for (let i = 0, j = str.length; i < j; ++i) {
-    arr.push(str.charCodeAt(i));
+    arr[i] = str.charCodeAt(i);
   }
-  let tmpUint8Array = new Uint8Array(arr);
-  return tmpUint8Array;
+  return arr;
 }
 
 function testConvertHmacKey() {