diff --git a/components/net/freemodbus/port/portserial.c b/components/net/freemodbus/port/portserial.c
index 7c546a1691..cbd846d7ff 100644
--- a/components/net/freemodbus/port/portserial.c
+++ b/components/net/freemodbus/port/portserial.c
@@ -52,6 +52,8 @@ static void serial_soft_trans_irq(void* parameter);
 BOOL xMBPortSerialInit(UCHAR ucPORT, ULONG ulBaudRate, UCHAR ucDataBits,
         eMBParity eParity)
 {
+    rt_device_t dev = RT_NULL;
+    char uart_name[20];
     /**
      * set 485 mode receive and transmit control IO
      * @note MODBUS_SLAVE_RT_CONTROL_PIN_INDEX need be defined by user
@@ -60,22 +62,19 @@ BOOL xMBPortSerialInit(UCHAR ucPORT, ULONG ulBaudRate, UCHAR ucDataBits,
     rt_pin_mode(MODBUS_SLAVE_RT_CONTROL_PIN_INDEX, PIN_MODE_OUTPUT);
 #endif
     /* set serial name */
-    if (ucPORT == 1) {
-#if defined(RT_USING_UART1) || defined(RT_USING_REMAP_UART1)
-        extern struct rt_serial_device serial1;
-        serial = &serial1;
-#endif
-    } else if (ucPORT == 2) {
-#if defined(RT_USING_UART2)
-        extern struct rt_serial_device serial2;
-        serial = &serial2;
-#endif
-    } else if (ucPORT == 3) {
-#if defined(RT_USING_UART3)
-        extern struct rt_serial_device serial3;
-        serial = &serial3;
-#endif
+    rt_snprintf(uart_name,sizeof(uart_name), "uart%d", ucPORT);
+
+    dev = rt_device_find(uart_name);
+    if(dev == RT_NULL)
+    {
+        /* can not find uart */
+        return FALSE;
     }
+    else
+    {
+        serial = (struct rt_serial_device*)dev;
+    }
+
     /* set serial configure parameter */
     serial->config.baud_rate = ulBaudRate;
     serial->config.stop_bits = STOP_BITS_1;
diff --git a/components/net/freemodbus/port/portserial_m.c b/components/net/freemodbus/port/portserial_m.c
index f68794a617..47a70dd905 100644
--- a/components/net/freemodbus/port/portserial_m.c
+++ b/components/net/freemodbus/port/portserial_m.c
@@ -53,6 +53,9 @@ static void serial_soft_trans_irq(void* parameter);
 BOOL xMBMasterPortSerialInit(UCHAR ucPORT, ULONG ulBaudRate, UCHAR ucDataBits,
         eMBParity eParity)
 {
+    rt_device_t dev = RT_NULL;
+    char uart_name[20];
+
     /**
      * set 485 mode receive and transmit control IO
      * @note MODBUS_MASTER_RT_CONTROL_PIN_INDEX need be defined by user
@@ -60,24 +63,20 @@ BOOL xMBMasterPortSerialInit(UCHAR ucPORT, ULONG ulBaudRate, UCHAR ucDataBits,
 #if defined(RT_MODBUS_MASTER_USE_CONTROL_PIN)
     rt_pin_mode(MODBUS_MASTER_RT_CONTROL_PIN_INDEX, PIN_MODE_OUTPUT);
 #endif
-
     /* set serial name */
-    if (ucPORT == 1) {
-#if defined(RT_USING_UART1) || defined(RT_USING_REMAP_UART1)
-        extern struct rt_serial_device serial1;
-        serial = &serial1;
-#endif
-    } else if (ucPORT == 2) {
-#if defined(RT_USING_UART2)
-        extern struct rt_serial_device serial2;
-        serial = &serial2;
-#endif
-    } else if (ucPORT == 3) {
-#if defined(RT_USING_UART3)
-        extern struct rt_serial_device serial3;
-        serial = &serial3;
-#endif
+    rt_snprintf(uart_name,sizeof(uart_name), "uart%d", ucPORT);
+
+    dev = rt_device_find(uart_name);
+    if(dev == RT_NULL)
+    {
+        /* can not find uart */
+        return FALSE;
     }
+    else
+    {
+        serial = (struct rt_serial_device*)dev;
+    }
+
     /* set serial configure parameter */
     serial->config.baud_rate = ulBaudRate;
     serial->config.stop_bits = STOP_BITS_1;