Aiming at the problem of difficult rotor heat dissipation in vacuum environment for drive motors for vacuum dry pumps, a hybrid excitation permanent magnet-reluctance composite synchronous motor is designed. The motor rotor permanent magnet excitation structure consists of two types of magnets, NdFeB and ferrite, aiming to change the arrangement of permanent magnets to reduce the loss of the motor. Firstly, the topology of the motor rotor is constructed, and two schemes are designed to study the influence of the arrangement of permanent magnets on the performance of the motor. Secondly, the effect of the rotor parameters on the no-load back electromotive force and electromagnetic torque of the motor is analyzed and the size of the motor rotor is adjusted. Thirdly, the losses of the two schemes are compared, and a low-loss motor scheme is selected. Finally, the temperature field analysis of the target motor is carried out by finite element calculation, and the results show that the motor temperature distribution of the designed scheme is reasonable, so the motor efficiency can be effectively improved by changing the arrangement of the permanent magnets, reducing the motor loss and ensuring the stable operation of the motor.