There is a phenomenon of vehicle overload in the transportation industry. The main purpose of this paper realizes real-time detection of vehicle load. Vehicle load causes the distance change between the axle and the frame. In order to detect vehicle load, the system uses magnetoresistance sensor to detect the distance change. And the system sends vehicle load information to the driver's handheld device and Beidou terminal. When the vehicle is overload, the system sends the alarm message to the driver's handheld device and Beidou terminal. The experiment shows that the system can detect vehicle load and realize overload alarm.