Abstract: In order to achieve high efficiency and energy saving, the permanent magnet synchronous motor is designed to replace the asynchronous motor to drive the rotary vane vacuum pump. Under the premise of ensuring that the vacuum degree of the system meets the standard, the motor speed is dynamically reduced based on the load demand, the change of motor performance parameters under the reduced speed condition is analyzed, and the energy-saving effect of the system is calculated. Through simulation analysis, the designed permanent magnet synchronous motor meets the first-level energy efficiency standard, and replacing the asynchronous motor can achieve high-efficiency energy saving; The temperature of each part of the motor is within the allowable range of the insulation grade, and the design is reasonable. The motor performance parameters change reasonably when the frequency is reduced to 10Hz; When the system vacuum meets the predetermined requirements, with the continuous reduction of motor speed, its energy-saving effect shows a significant improvement trend.