Finite element simulation was adopted to analyze the radial air gap flux density and the radial electromagnetic exciting force wave of a 16slot 96pole surface mounted permanent magnet synchronous motor (PMSM) under the straight and skewed slots couditions. The noload vibration of these two structures was simulated through coupled harmonic response analysis. The accuracy correctness of the simulation was proved by experiment. The expecnnest result showed that the noload vibration frequency matched the frequency of the force wave. The amplitude of the loworder force wave especially whose order equalled the slot number could be effectively reduced by using skewed slots, and the vibration of the PMSM was effectively reduced as well.