Highspeed permanent synchronous motor speed sensorless control had become a trend. When using the traditional model reference adaptive system (MRAS), due to the use of integral calculation, there were problems such as zero drift and phase shift in the flux linkage observation. An improved method was proposed. The voltage model and the current model flux linkage observation results were subtracted, and the error value was adjusted by the PI to compensate the voltage in the voltage model, which solved the above problem well and had excellent control performance. The simulation model was built in MATLAB/Simulink to verify the proposed method. Simulation results showed that the improved MRAS could accurately track the rotor speed and position over the full speed range, and it could still run stably under sudden load changes.