In order to study the characteristics of an asymmetric surface mounted permanent magnet synchronous motor(SPMSM),an analytical calculation model of magnetic field was established by taking an unequal pole 8-poles 36-slots SPMSM as an example,and the analytical results of magnetic flux density were compared with the finite element method results.The accuracy of the analytical model is verified.Based on the analytical model,the characteristics of air gap magnetic field,no-load back electromotive force (EMF),on-load output torque,electromagnetic force waves and rotor shaft unbalance electromagnetic force of the unequal pole motor were compared with those of the equal pole motor,the loss characteristics were analyzed based on the finite element method.The vibration acceleration of the unequal pole motor was measured,the vibration characteristics of the motor were studied,and the validity of the electromagnetic force waves analysis was furtherly verified.The results show that the asymmetric magnetic poles structure can effectively reduce the torque ripple of the motor.However,it will affect the performance of other aspects of the motor.