The AC permanent-magnet synchronous motor with characteristics of high efficiency, high stability, long using life and simple maintenance is one of the most important developing directions in the motor field. The research on electromagnetic vibration is foundations of designing the low noising AC permanent-magnet synchronous motor. In this paper, starting from the structure of AC permanent-magnet synchronous motor, the magnetic flux density, radial electromagnetic force and vibration’s theoretical model of the three-phase AC permanent-magnet synchronous motor were deduced. Influencing factors of the electromagnetic vibration of permanent-magnet synchronous motor were analyzed from the theoretical point of view. The main frequency of electromagnetic vibration was put forward. To analyze the distribution of the electromagnetic field accurately, the three-phase AC permanent-magnet synchronous motor with 4 poles and 24 slots was simulated by numerical simulation of magnetic field, obtaining the radial flux density. By theoretical modeling and the numerical simulation of the magnetic field, the simulation results showed that when slots of the permanent-magnet synchronous motor was close to 2 times, 4 times, 6 times or 8 times of motor poles, the motor generated vibration frequency which is 2 times, 4 times or 6 times as the fundamental frequency
