The fractional-slot permanent magnet synchronous motor has high electromagnetic noise due to its lower order radial electromagnetic force. Based on theoretical analysis, Optislang multi-objective optimization platform and Ansys multi-physics-field finite element analysis platform, the electromagnetic noise of an 8-pole 36-slot permanent magnet synchronous motor for electric vehicle is analyzed and optimized. The electromagnetic noise of the motor is mainly caused by the vibration deformation of the stator core caused by the radial electromagnetic force acting on the stator teeth. The radial electromagnetic force is weakened by opening the auxiliary slots on the stator teeth and optimizing the slot parameters. The 2D finite element model of the motor is established, and the parameters of stator auxiliary slots on the stator teeth under different working conditions are optimized by Optislang, the Pareto front is calculated and the relative optimal solution is found. The radial electromagnetic forces of the stator teeth before and after the motor optimization are compared and analyzed, mapped to the corresponding 3D structure, and the electromagnetic noises before and after the motor optimization is calculated by Ansys. The effectiveness of the simulation results is verified by the prototype noise test.