In order to obtain a precise model of permanent magnet synchronous motor (PMSM)，a fractional-order
modeling approach of PMSM is proposed by combining the mechanism modeling and the numerical modeling． First，the model structures of electromagnetic part and mechanical part of PMSM are built on the basis of the composition mechanism of PMSM，and modeling experiments are conducted on the two parts． Then，the parameters of the two parts are identified by applying the output-error numerical fitting method，and the fractional-order model of PMSM is thus obtained． Finally，the speed controllers are designed on the basis of the obtained model，and the simulations and experiments of tracking the motor speed are performed． Simulation and experimental results show that the proposed fractional-order model can describe the nature of PMSM more precisely in comparison with the integer-order model．