In order to solve the pole frequency vibration problem of a 10-pole and 12-slot surface-mount permanent magnet synchronous motor, a weakening scheme of the pole structure with axially unequal width is proposed. This scheme can effectively reduce the extreme frequency vibration of the motor under the premise of ensuring the torque density of the motor. Firstly, based on the Maxwell stress tensor method, an analytical expression for the radial electromagnetic force of the motor is derived, and a model of the electromagnetic force acting on the stator teeth of the motor is established. Simultaneously, factors contributing to the generation of pole frequency electromagnetic force harmonics in the prototype are analyzed. Then, through finite element simulation analysis, the basic mechanism of reducing pole frequency electromagnetic force by using the magnetic pole structure with axially unequal width is explained. And comparison analysis of the motor′s electromagnetic performance and vibration acceleration before and after optimization is conducted. Finally, the results show that the polar structure with axially unequal width can effectively reduce the harmonics and vibrations of the polar electromagnetic force while maintaining the torque density of the motor, which confirms the effectiveness of the optimization scheme.