The heat dissipation of the vacuum dry pump drive motor is difficult, and it is necessary to strictly control its temperature rise to ensure the long-term operation of the system. Taking a 30 kW drive motor as the research object, an asynchronous motor and an 18/12 pole double salient permanent magnet motor are designed. The external dimensions and power levels of the two motors are the same. At the same time, the cooling mode of the two motors is water cooling with spiral water channel in the casing, and the temperature fields of the two motors are analyzed respectively. The analysis results show that the doubly salient permanent magnet motor has a lower overall temperature rise during the rated operation, which is more suitable for the vacuum dry pump units.