diff --git a/src/import/mdm9206/example/iotkit_demo.c b/src/import/mdm9206/example/iotkit_demo.c
index 0de0d72da..62c83f1fc 100644
--- a/src/import/mdm9206/example/iotkit_demo.c
+++ b/src/import/mdm9206/example/iotkit_demo.c
@@ -109,8 +109,8 @@ static const QCLI_Command_t iot_cmd_list[] =
             "       p <topic> <message>  #publish\n"
             "       s <topic> #subscribe\n"
             "       u <topic> #unsubscribe\n"
-            "       y #yield\n"
-            "       d ", "test mqtt function",NULL},
+            "       y <timeout> or y#yield\n"
+            "       d #destroy", "test mqtt function",NULL},
 
     {http, false, "http", "#i <key><secret><name><id> or i#init\n"
         "       a #auth\n"
@@ -147,10 +147,11 @@ static QCLI_Command_Status_t mqtt(uint32_t Parameter_Count, QCLI_Parameter_t *Pa
 #define MQTT_DEVICE_NAME_LEN        (32)
 #define MQTT_DEVICE_SECRET_LEN      (64)
 
+    static char isInit = 0;
     static char msg_buf[MSG_LEN_MAX];
     static char msg_readbuf[MSG_LEN_MAX] ;
 
-    static iotx_conn_info_pt pconn_info;
+    static iotx_conn_info_pt pconn_info = NULL;
     static iotx_mqtt_param_t mqtt_params;
     static void *pclient=NULL;
     char command = '0';
@@ -162,6 +163,17 @@ static QCLI_Command_Status_t mqtt(uint32_t Parameter_Count, QCLI_Parameter_t *Pa
     if(Parameter_Count < 1){
         return QCLI_STATUS_USAGE_E;
     }
+
+    if(isInit == 0){
+        memset(msg_buf, 0, sizeof(msg_buf));
+        memset(msg_readbuf, 0, sizeof(msg_readbuf));
+        memset(&mqtt_params, 0, sizeof(mqtt_params));
+        memset(product_key, 0, sizeof(product_key));
+        memset(device_name, 0, sizeof(device_name));
+        memset(device_secret, 0, sizeof(device_secret));
+        isInit = 1;
+    }
+
     command = (char)Parameter_List[0].String_Value[0];
 
     switch ( command ) {
@@ -231,7 +243,7 @@ static QCLI_Command_Status_t mqtt(uint32_t Parameter_Count, QCLI_Parameter_t *Pa
                     QCLI_Printf(qcli_iotkit_handle, "had constructed\n");
                     break;
                 }
-                if (pconn_info->client_id == 0){
+                if ((NULL == pconn_info) || (0 == pconn_info->client_id)){
                     QCLI_Printf(qcli_iotkit_handle, "please auth first\n");
                     break;
                 }
@@ -363,6 +375,7 @@ static QCLI_Command_Status_t http(uint32_t Parameter_Count, QCLI_Parameter_t *Pa
 {
     static void *http_handle = NULL;
 
+    static char isInit = 0;
     static iotx_device_info_t device_info;
     static iotx_http_param_t http_param;
 
@@ -372,6 +385,12 @@ static QCLI_Command_Status_t http(uint32_t Parameter_Count, QCLI_Parameter_t *Pa
         return QCLI_STATUS_USAGE_E;
     }
 
+    if(0 == isInit){
+        memset(&device_info, 0, sizeof(device_info));
+        memset(&http_param, 0 ,sizeof(http_param));
+        isInit = 1;
+    }
+
     command = (char)Parameter_List[0].String_Value[0];
 
     switch ( command ) {
diff --git a/src/import/mdm9206/example/iotkit_hal.c b/src/import/mdm9206/example/iotkit_hal.c
index 033a6d70c..280f593ed 100644
--- a/src/import/mdm9206/example/iotkit_hal.c
+++ b/src/import/mdm9206/example/iotkit_hal.c
@@ -8,6 +8,8 @@
 #define _IN_
 #define _OU_
 
+#define LOG_BUFFER_SIZE 256
+
 extern QCLI_Group_Handle_t qcli_iotkit_handle;     /* Handle for IOT Command Group. */
 
 int HAL_Vsnprintf(_IN_ char *str, _IN_ const int len, _IN_ const char *format, va_list ap)
@@ -17,12 +19,15 @@ int HAL_Vsnprintf(_IN_ char *str, _IN_ const int len, _IN_ const char *format, v
 
 void HAL_Printf(_IN_ const char *fmt, ...)
 {
-    static char str_tmp[256] = {0};
+    static char str_tmp[LOG_BUFFER_SIZE];
     va_list list;
-    va_start (list, fmt);
-    HAL_Vsnprintf(str_tmp, 256, fmt, list);
+
+    memset(str_tmp, 0, LOG_BUFFER_SIZE);
+
+    va_start(list, fmt);
+    HAL_Vsnprintf(str_tmp, LOG_BUFFER_SIZE - 1, fmt, list);
     va_end(list);
-    QCLI_Printf(qcli_iotkit_handle, "%s",str_tmp);
+    QCLI_Printf(qcli_iotkit_handle, "%s", str_tmp);
 }
 
 int HAL_Snprintf(_IN_ char *str, const int len, const char *fmt, ...)
@@ -37,7 +42,8 @@ int HAL_Snprintf(_IN_ char *str, const int len, const char *fmt, ...)
     return rc;
 }
 
-char *HAL_GetModuleID(char mid_str[]){
+char *HAL_GetModuleID(char mid_str[])
+{
     strcpy(mid_str, "xyz");
     return "xyz";
 }
@@ -53,9 +59,10 @@ uint32_t HAL_Random(uint32_t region)
     return (region > 0) ? (rand() % region) : 0;
 }
 
-int HAL_Atoi(const char *str){
-    int res = 0,i;
-    for(i = 0 ; str[i] <='9' && str[i] >= '0';++i){
+int HAL_Atoi(const char *str)
+{
+    int res = 0, i;
+    for (i = 0 ; str[i] <= '9' && str[i] >= '0'; ++i) {
         res = res * 10 + str[i] - '0';
     }
     return res;