Abstract: Due to the running status and characteristics of the electric machines are directly related to its electrical, magnetic, thermal and other physical fields, multiple physical field coupling analysis is of great importance. In this paper, 3D finite element method is used to research on magnetic field distribution when the fractional slot permanent magnet machine running, and get loss values by magnetic field analysis. Taking each part of the loss as a heat source of the electric machine in the simulation analysis of temperature field of permanent magnet machine and got the temperature distribution of the machine. Then a prototype machine is used to experiment based on this. The validity of the multiple physical field coupling analysis method is confirmed through the comparison of the experimental results with the simulation results, laid a theoretical basis for the subsequent electric machine structure optimization.