Aiming at the problems of high rotor temperature and difficult heat dissipation during the operation of the drive motor for vacuum pump, a negative salient pole permanent magnet synchronous motor and a conventional permanent magnet synchronous motor are designed according to the actual requirements of the driving conditions of vacuum pump. Firstly, the impact of the size of the rotor magnetic barrier on the motor torque and the impact of the number of magnetic barrier layers on the inductance are analyzed using finite element software, so the suitable values of the rotor magnetic barrier size and the number of magnetic barrier layers are obtained. Secondly, the electromagnetic performances of the two motors, such as the air gap magnetic density waveforms, no-load back electromotive force and losses are comparatively analyzed. Finally, the temperature fields of the two motors as well as the temperature rises at the rotors and shafts of the two motors are analyzed by simulation comparison. The results show that compared with the conventional permanent magnet synchronous motor, the negative salient pole permanent magnet synchronous motor has better torque performance, smaller rotor loss and rotor temperature rise, which provides a scientific reference for the development of new products.