diff --git a/runner-core/src/main/java/org/apache/apisix/plugin/runner/handler/RpcCallHandler.java b/runner-core/src/main/java/org/apache/apisix/plugin/runner/handler/RpcCallHandler.java
index ed5ff040..f054ccfe 100644
--- a/runner-core/src/main/java/org/apache/apisix/plugin/runner/handler/RpcCallHandler.java
+++ b/runner-core/src/main/java/org/apache/apisix/plugin/runner/handler/RpcCallHandler.java
@@ -215,7 +215,7 @@ private void doPostFilter(ChannelHandlerContext ctx) {
     }
 
     private void handleExtraInfo(ChannelHandlerContext ctx, ExtraInfoResponse request) {
-        String result = request.getResult();
+        byte[] result = request.getResult();
         String varsKey = queue.poll();
         if (Objects.isNull(varsKey)) {
             logger.error("queue is empty");
@@ -233,7 +233,7 @@ private void handleExtraInfo(ChannelHandlerContext ctx, ExtraInfoResponse reques
             }
         }
         else {
-            nginxVars.put(varsKey, result);
+            nginxVars.put(varsKey, new String(result));
         }
 
         if (queue.isEmpty()) {
diff --git a/runner-plugin-sdk/src/main/java/org/apache/apisix/plugin/runner/ExtraInfoResponse.java b/runner-plugin-sdk/src/main/java/org/apache/apisix/plugin/runner/ExtraInfoResponse.java
index eb10f975..7839afb1 100644
--- a/runner-plugin-sdk/src/main/java/org/apache/apisix/plugin/runner/ExtraInfoResponse.java
+++ b/runner-plugin-sdk/src/main/java/org/apache/apisix/plugin/runner/ExtraInfoResponse.java
@@ -35,12 +35,12 @@ public static ExtraInfoResponse from(ByteBuffer buffer) {
         return new ExtraInfoResponse(req);
     }
 
-    public String getResult() {
-        StringBuilder builder = new StringBuilder();
+    public byte[] getResult() {
+        byte[] byteArray = new byte[this.resp.resultLength()];
         for (int i = 0; i < this.resp.resultLength(); i++) {
-            builder.append((char) this.resp.result(i));
+            byteArray[i] = (byte) this.resp.result(i);
         }
-        return builder.toString();
+        return byteArray;
     }
 
     @Override
diff --git a/runner-plugin-sdk/src/main/java/org/apache/apisix/plugin/runner/HttpRequest.java b/runner-plugin-sdk/src/main/java/org/apache/apisix/plugin/runner/HttpRequest.java
index 896a9118..2efede05 100644
--- a/runner-plugin-sdk/src/main/java/org/apache/apisix/plugin/runner/HttpRequest.java
+++ b/runner-plugin-sdk/src/main/java/org/apache/apisix/plugin/runner/HttpRequest.java
@@ -24,6 +24,7 @@
 import org.springframework.util.StringUtils;
 
 import java.nio.ByteBuffer;
+import java.nio.charset.Charset;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Objects;
@@ -50,7 +51,7 @@ public class HttpRequest implements A6Request {
 
     private Map<String, String> vars;
 
-    private String body;
+    private byte[] body;
 
     public HttpRequest(Req req) {
         this.req = req;
@@ -300,10 +301,18 @@ public void setVars(Map<String, String> vars) {
     }
 
     public String getBody() {
-        return body;
+        return new String(body);
+    }
+
+    public String getBody(Charset charset) {
+        return new String(body, charset);
     }
 
     public void setBody(String body) {
+        this.body = body.getBytes();
+    }
+
+    public void setBody(byte[] body) {
         this.body = body;
     }
 
diff --git a/runner-plugin-sdk/src/main/java/org/apache/apisix/plugin/runner/PostRequest.java b/runner-plugin-sdk/src/main/java/org/apache/apisix/plugin/runner/PostRequest.java
index ba4179ad..88315f59 100644
--- a/runner-plugin-sdk/src/main/java/org/apache/apisix/plugin/runner/PostRequest.java
+++ b/runner-plugin-sdk/src/main/java/org/apache/apisix/plugin/runner/PostRequest.java
@@ -23,6 +23,7 @@
 import org.springframework.util.CollectionUtils;
 
 import java.nio.ByteBuffer;
+import java.nio.charset.Charset;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Objects;
@@ -38,7 +39,7 @@ public class PostRequest implements A6Request {
 
     private Integer status;
 
-    private String body;
+    private byte[] body;
 
     private Map<String, String> vars;
 
@@ -94,11 +95,19 @@ public Integer getUpstreamStatusCode() {
     }
 
     public void setBody(String body) {
+        this.body = body.getBytes();
+    }
+
+    public void setBody(byte[] body) {
         this.body = body;
     }
 
     public String getBody() {
-        return body;
+        return new String(body);
+    }
+
+    public String getBody(Charset charset) {
+        return new String(body, charset);
     }
 
     public String getVars(String key) {
diff --git a/runner-plugin-sdk/src/test/java/org/apache/apisix/plugin/runner/PostResponseTest.java b/runner-plugin-sdk/src/test/java/org/apache/apisix/plugin/runner/PostResponseTest.java
index 512aca96..1c8a4de8 100644
--- a/runner-plugin-sdk/src/test/java/org/apache/apisix/plugin/runner/PostResponseTest.java
+++ b/runner-plugin-sdk/src/test/java/org/apache/apisix/plugin/runner/PostResponseTest.java
@@ -1,3 +1,20 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 package org.apache.apisix.plugin.runner;
 
 import org.junit.jupiter.api.DisplayName;