In order to reduce the permanent magnet synchronous motor cogging torque and improve the motor output performance, a method of motor stator slot offset was proposed with the example of 3-phase 8-pole 36-slot built-in combined permanent magnet synchronous motor. Firstly, a mathematical model of motor stator slot offset was established by theoretically deriving the stator tooth air gap permeability function. Secondly, the effects of peak cogging torque, output torque and torque pulsation at different offset angles under different numbers of stator slot offsets were analyzed, and adaptive genetic algorithms were used to determine the target values under the offset angles for the number of stator slot offsets. Finally, a trial prototype was produced and the experiment was conducted. The results show that the peak cogging torque of the optimized motor is reduced by 49.56%, the torque pulsation is reduced by 39.2%, the average output torque is appropriately improved, and the air-gap magnetic density harmonics are appropriately reduced; the average output torque increases and the motor output performance is improved. The proposed stator slot offset structure and multi-objective joint simulation method are rational and effective, which can provide some reference for cogging torque optimization and output performance improvement of the same type of motors.