diff --git a/class/bc26/at_device_bc26.c b/class/bc26/at_device_bc26.c
index 7dcc43a..7657b51 100644
--- a/class/bc26/at_device_bc26.c
+++ b/class/bc26/at_device_bc26.c
@@ -40,8 +40,6 @@ static int bc26_power_on(struct at_device *device)
 {
     struct at_device_bc26 *bc26 = RT_NULL;
     
-    RT_ASSERT(device);
-
     bc26 = (struct at_device_bc26 *)device->user_data;
     bc26->power_status = RT_TRUE;
 
@@ -63,8 +61,6 @@ static int bc26_power_off(struct at_device *device)
     at_response_t resp = RT_NULL;
     struct at_device_bc26 *bc26 = RT_NULL;
     
-    RT_ASSERT(device);
-
     resp = at_create_resp(64, 0, rt_tick_from_millisecond(300));
     if (resp == RT_NULL)
     {
@@ -91,8 +87,6 @@ static int bc26_sleep(struct at_device *device)
 {
     at_response_t resp = RT_NULL;
     struct at_device_bc26 *bc26 = RT_NULL;
-
-    RT_ASSERT(device);
     
     bc26 = (struct at_device_bc26 *)device->user_data;
     if ( ! bc26->power_status)//power off
@@ -135,9 +129,7 @@ static int bc26_wakeup(struct at_device *device)
 {
     at_response_t resp = RT_NULL;
     struct at_device_bc26 *bc26 = RT_NULL;
-
-    RT_ASSERT(device);
-
+    
     bc26 = (struct at_device_bc26 *)device->user_data;
     if ( ! bc26->power_status)//power off
     {
@@ -182,16 +174,13 @@ static int bc26_check_link_status(struct at_device *device)
     at_response_t resp = RT_NULL;
     struct at_device_bc26 *bc26 = RT_NULL;
     int result = -RT_ERROR;
-
-    RT_ASSERT(device);
-
+    
+    bc26 = (struct at_device_bc26 *)device->user_data;
     if ( ! bc26->power_status)//power off
     {
         LOG_D("the power is off.");
         return(-RT_ERROR);
     }
-
-    bc26 = (struct at_device_bc26 *)device->user_data;
     if (bc26->sleep_status)//is sleep status
     {
         if (bc26->power_pin != -1)
@@ -874,8 +863,11 @@ static int bc26_net_init(struct at_device *device)
 
 static int bc26_init(struct at_device *device)
 {
-    struct at_device_bc26 *bc26 = (struct at_device_bc26 *) device->user_data;
-
+    struct at_device_bc26 *bc26 = RT_NULL;
+    
+    RT_ASSERT(device);
+    
+    bc26 = (struct at_device_bc26 *) device->user_data;
     bc26->power_status = RT_FALSE;//default power is off.
     bc26->sleep_status = RT_FALSE;//default sleep is disabled.
 
@@ -915,6 +907,8 @@ static int bc26_init(struct at_device *device)
 
 static int bc26_deinit(struct at_device *device)
 {
+    RT_ASSERT(device);
+    
     return bc26_netdev_set_down(device->netdev);
 }
 
diff --git a/class/bc26/at_socket_bc26.c b/class/bc26/at_socket_bc26.c
index b490738..042a003 100644
--- a/class/bc26/at_socket_bc26.c
+++ b/class/bc26/at_socket_bc26.c
@@ -446,8 +446,7 @@ static int bc26_domain_resolve(const char *name, char ip[16])
     int i, result;
     at_response_t resp = RT_NULL;
     struct at_device *device = RT_NULL;
-    struct at_device_bc26 *bc26 = (struct at_device_bc26 *) device->user_data;
-    char *recv_ip = (char *) bc26->socket_data;
+    struct at_device_bc26 *bc26 = RT_NULL;
 
     RT_ASSERT(name);
     RT_ASSERT(ip);
@@ -489,10 +488,7 @@ static int bc26_domain_resolve(const char *name, char ip[16])
         }
         else
         {
-            //struct at_device_bc26 *bc26 = (struct at_device_bc26 *) device->user_data;
-            //char *recv_ip = (char *) bc26->socket_data;
-
-            if (rt_strlen(recv_ip) < 8)
+            if (rt_strlen(ip) < 8)
             {
                 rt_thread_mdelay(100);
                 /* resolve failed, maybe receive an URC CRLF */
@@ -501,8 +497,6 @@ static int bc26_domain_resolve(const char *name, char ip[16])
             }
             else
             {
-                //rt_strncpy(ip, recv_ip, 15);
-                //ip[15] = '\0';
                 result = RT_EOK;
                 break;
             }
@@ -510,6 +504,7 @@ static int bc26_domain_resolve(const char *name, char ip[16])
     }
 
  __exit:
+    bc26->socket_data = RT_NULL;
     if (resp)
     {
         at_delete_resp(resp);
@@ -576,6 +571,7 @@ static void urc_send_func(struct at_client *client, const char *data, rt_size_t
         LOG_E("get device(%s) failed.", client_name);
         return;
     }
+    
     bc26 = (struct at_device_bc26 *) device->user_data;
     device_socket = (int) bc26->user_data;