diff --git a/bsp/src/bsp_mq.c b/bsp/src/bsp_mq.c
index 321d811..4bd49fd 100644
--- a/bsp/src/bsp_mq.c
+++ b/bsp/src/bsp_mq.c
@@ -120,7 +120,7 @@ static uint8_t Sensor_CheckData(void)
 
     if(alarm_flag)
     {
-        alarm_status_buffer[index] = ((voltage > Sensor_device.alarm_value - 50) && (voltage < MQ_VOLTAGE_HIGH_LIMIT)) ? kSensorAlarm : kSensorNormal;
+        alarm_status_buffer[index] = ((voltage > (Sensor_device.alarm_value - 50)) && (voltage < MQ_VOLTAGE_HIGH_LIMIT)) ? kSensorAlarm : kSensorNormal;
     }
     else
     {