The change of the main magnetic field caused by the interference of the permanent magnet motor stator will cause the performance of the actual motor to deviate from the design value. The influence of interference on the stress and strain of stator core is studied according to the ferromagnetism theory and magnetic circuit law to optimize the design. The solution model is established and the simulation calculation and experiment are carried out based on a 560 kW motor. The analysis results in this paper can be used for reference in the optimization design of permanent magnet motor.