diff --git a/src/main/java/com/iot/modbus_rtcp/netty/ModbusSender.java b/src/main/java/com/iot/modbus_rtcp/netty/ModbusSender.java
index 43e3aef..5810123 100644
--- a/src/main/java/com/iot/modbus_rtcp/netty/ModbusSender.java
+++ b/src/main/java/com/iot/modbus_rtcp/netty/ModbusSender.java
@@ -46,7 +46,7 @@ public class ModbusSender {
             if (modbusCommandBo.getIdentifier() == null) {
                 throw new NullPointerException("Invalid gateway identifier");
             }
-            if (!ModbusFunctionCodeEnums.isHandlerHexCode(StringUtils.substring(modbusCommandBo.getCommand(), 2, 2))) {
+            if (!ModbusFunctionCodeEnums.isHandlerHexCode(StringUtils.substring(modbusCommandBo.getCommand(), 2, 4))) {
                 throw new RuntimeException("Not support command: " + modbusCommandBo.getCommand());
             }
 
diff --git a/src/main/java/com/iot/modbus_rtcp/netty/SyncHandler.java b/src/main/java/com/iot/modbus_rtcp/netty/SyncHandler.java
index aba87cd..fb99b46 100644
--- a/src/main/java/com/iot/modbus_rtcp/netty/SyncHandler.java
+++ b/src/main/java/com/iot/modbus_rtcp/netty/SyncHandler.java
@@ -56,7 +56,7 @@ public class SyncHandler extends ChannelInboundHandlerAdapter {
             return;
         }
 
-        if (!ModbusFunctionCodeEnums.isHandlerHexCode(StringUtils.substring(msg.toString(), 2, 2))) {
+        if (!ModbusFunctionCodeEnums.isHandlerHexCode(StringUtils.substring(msg.toString(), 2, 4))) {
             log.warn("Gateway {} fails to send command {} to return data: {}",
                     channel.getIdentifier(), message.getCommand(), msg);
             // TODO 可在此处添加设备告警
diff --git a/src/main/java/com/iot/modbus_rtcp/utils/ModbusFunctionCodeEnums.java b/src/main/java/com/iot/modbus_rtcp/utils/ModbusFunctionCodeEnums.java
index 0f9e803..f5a309a 100644
--- a/src/main/java/com/iot/modbus_rtcp/utils/ModbusFunctionCodeEnums.java
+++ b/src/main/java/com/iot/modbus_rtcp/utils/ModbusFunctionCodeEnums.java
@@ -2,6 +2,7 @@ package com.iot.modbus_rtcp.utils;
 
 import com.iot.modbus_rtcp.dto.CommandTypeComparable;
 import lombok.Getter;
+import org.apache.commons.lang3.StringUtils;
 
 import java.util.Arrays;
 import java.util.Collection;
@@ -40,24 +41,24 @@ public enum ModbusFunctionCodeEnums {
         this.description = description;
     }
 
-    public String getHexCode() {
-        return Integer.toHexString(this.code);
+    public String getFunctionCode() {
+        return StringUtils.leftPad(Integer.toHexString(this.code), 2, "0");
     }
 
-    public static Collection<ModbusFunctionCodeEnums> getAllControlCode() {
+    public static Collection<ModbusFunctionCodeEnums> getAllControlFunctionCode() {
         return Arrays.stream(values())
                 .filter(item -> Objects.equals(CommandTypeComparable.CommandType.CONTROL, item.getCommandType()))
                 .toList();
     }
 
-    public static Collection<ModbusFunctionCodeEnums> getAllCollectionCode() {
+    public static Collection<ModbusFunctionCodeEnums> getAllCollectionFunctionCode() {
         return Arrays.stream(values())
                 .filter(item -> Objects.equals(CommandTypeComparable.CommandType.COLLECTION, item.getCommandType()))
                 .toList();
     }
 
     public static boolean isHandlerHexCode(String hexCode) {
-        return Arrays.stream(values()).anyMatch(item -> Objects.equals(item.getHexCode(), hexCode));
+        return Arrays.stream(values()).anyMatch(item -> StringUtils.equalsIgnoreCase(item.getFunctionCode(), hexCode));
     }
 
 }
diff --git a/src/test/java/com/iot/modbus_rtcp/BinaryToDecimalTest.java b/src/test/java/com/iot/modbus_rtcp/BinaryToDecimalTest.java
index 1997f2f..adc3beb 100644
--- a/src/test/java/com/iot/modbus_rtcp/BinaryToDecimalTest.java
+++ b/src/test/java/com/iot/modbus_rtcp/BinaryToDecimalTest.java
@@ -1,5 +1,7 @@
 package com.iot.modbus_rtcp;
 
+import com.iot.modbus_rtcp.utils.ModbusFunctionCodeEnums;
+import org.apache.commons.lang3.StringUtils;
 import org.junit.jupiter.api.Test;
 
 /**
@@ -8,6 +10,21 @@ import org.junit.jupiter.api.Test;
  */
 public class BinaryToDecimalTest {
 
+    @Test
+    public void testIsHandlerHexCode() throws Exception {
+        System.out.println(ModbusFunctionCodeEnums.isHandlerHexCode("01"));
+        System.out.println(ModbusFunctionCodeEnums.isHandlerHexCode("02"));
+        System.out.println(ModbusFunctionCodeEnums.isHandlerHexCode("03"));
+        System.out.println(ModbusFunctionCodeEnums.isHandlerHexCode("04"));
+        System.out.println(ModbusFunctionCodeEnums.isHandlerHexCode("05"));
+        System.out.println(ModbusFunctionCodeEnums.isHandlerHexCode("06"));
+        System.out.println(ModbusFunctionCodeEnums.isHandlerHexCode("0F"));
+        System.out.println(ModbusFunctionCodeEnums.isHandlerHexCode("10"));
+        System.out.println(ModbusFunctionCodeEnums.isHandlerHexCode(StringUtils.substring("010400000016", 2, 4)));
+        System.out.println(ModbusFunctionCodeEnums.isHandlerHexCode(StringUtils.substring("010300640052", 2, 4)));
+        System.out.println(ModbusFunctionCodeEnums.isHandlerHexCode(StringUtils.substring("010200140004 ", 2, 4)));
+    }
+
     @Test
     public void binaryNegative() {
         int number = 225;