In order to improve the torque control performance of permanent magnet synchronous motor, variable frequency variable speed control technology, vector control technology, direct torque control technology and sensorless control technology were analyzed. The fuzzy + PID control technology used in permanent magnetic synchronous motor was introduced in detail. The conventional sliding mode observer based on the counter electromotive force estimate control technology and the structure of improved sliding mode observer was given separately. The fuzzy + PID control technology and improved sliding mode observer control technology proposed could improve the dynamic performance and static performance of the permanent magnet synchronous motor.