Aiming at identifying motor speed of the permanent magnet synchronous motor in an accurate manner, a method based on variable structure MARS is proposed. The slidingmode observer is designed and the sliding mode variable structure is added by establishing mathematical models of PMSM, using the motor as a reference model, and adopting stator current as an adjustable model. In the MATLAB/Simulink, make an emulation test for the adaptive system of the nosensor controller in PMSM model. Through observation and analysis of the rotator’s actual speed and the estimated speed curve,a conclusion is drawn that this system can accurately estimate rotor speed with static performance.