Several key technologies were introduced in the development of the air-gap magnetic field measurement system of high-speed magnetic levitation vehicle. The design method of the three-dimensional magnetic sensors and the voltage proportional magnetic field measurement method based on Hall-effect devices were put forward in this paper. It also presented a motion control system with high precision designed for the sensor. The research shows that the developed system has high measurement and orientation precision, and it can perform automatic measurement of the air gap magnetic fields of high speed magnetic levitation vehicle.