Permanent magnet synchronous motor has been an important role in production and life because of its low loss, small size and high power, but it also has the problem of torque ripple. Reducing torque ripple is one of the important contents in the research and design of permanent magnet synchronous motor. Therefore, in order to inhibit the torque ripple, this paper optimized the motor design starting from the cogging torque based on the stator tooth crown slotting method. The 14-pole 12-slot permanent magnet synchronous motor is used as experimental subject, and this paper analyzes the effect of opening auxiliary slots on the torque of the motor tooth ripple, and optimizes the size and position of the auxiliary slots by coordinate rotation method. Finally, the torque fluctuation of the motor is reduced from 6.19% to 2.45%.