diff --git a/code/application/source/sf_app/code/include/sf_hal_ttyusb.h b/code/application/source/sf_app/code/include/sf_hal_ttyusb.h
index ceca11920..c3744ac23 100755
--- a/code/application/source/sf_app/code/include/sf_hal_ttyusb.h
+++ b/code/application/source/sf_app/code/include/sf_hal_ttyusb.h
@@ -89,6 +89,8 @@ SINT32 sf_hal_uart_deinit(void);
 
 SINT32 sf_hal_ttyusb2_read_buf(SF_TTY_DATA_TYPE_S *recv);
 
+SINT32 sf_get_ttyusb_flag(void);
+
 #ifdef __cplusplus
 #if __cplusplus
 }
diff --git a/code/application/source/sf_app/code/source/app/sf_service.c b/code/application/source/sf_app/code/source/app/sf_service.c
index 46284d271..7fd85af55 100755
--- a/code/application/source/sf_app/code/source/app/sf_service.c
+++ b/code/application/source/sf_app/code/source/app/sf_service.c
@@ -99,7 +99,7 @@ SINT32 app_ttyusb_IsOpen(void) {
     static SINT32 s32ret = SF_SUCCESS;
     static int flag = 0;
 
-    if(flag)
+    if((flag) && (sf_get_ttyusb_flag()))
     {
         return s32ret;
     }
diff --git a/code/application/source/sf_app/code/source/ttyusb/sf_hal_ttyusb.c b/code/application/source/sf_app/code/source/ttyusb/sf_hal_ttyusb.c
index 72f74ab2b..744a6dd10 100755
--- a/code/application/source/sf_app/code/source/ttyusb/sf_hal_ttyusb.c
+++ b/code/application/source/sf_app/code/source/ttyusb/sf_hal_ttyusb.c
@@ -457,6 +457,12 @@ SINT32 sf_hal_ttyusb2_read_buf(SF_TTY_DATA_TYPE_S *recv)
 	return SF_SUCCESS;
 }
 
+
+SINT32 sf_get_ttyusb_flag(void)
+{
+    return TtyUSB2Fd;
+}
+
 #ifdef __cplusplus
 #if __cplusplus
 }