Permanent magnet brushless DC motor (PMBDC) has been widely used as a micro motor in automotive industry.However,the cogging torque of permanent magnet motor will cause vibration and noise,which will reduce the control accuracy of the system.Based on the cogging torque generation mechanism,combined with energy method and Fourier decomposition method,the mathematical expression of the cogging torque of permanent magnet brushless DC motor with auxiliary slots on the rotor teeth was derived.Based on Ansoft Maxwell,the influence of the number,location,width,depth and shape of the auxiliary slots on the cogging torque of the rotor teeth of the lifter motor of a certain vehicles tail gate was analyzed.The relationship between the parameters of the auxiliary slot and the peak value of the cogging torque was obtained,and the reasonable values of the parameters were determined.The optimization results show that the cogging torque of the sample motor is effectively suppressed.