The lightweight design of a certain type of permanent magnet synchronous wheel-side motor for bus is analyzed. The scheme and principle of the lightweight design of the motor are put forward, and the lightweight design of rotor end plate, rotor punching, casing and back-end cover of the motor is carried out. The finite element analysis software is used for the modal analysis of the lightweight motor rotor, and the random vibration of the wheel-side motor is analyzed by finite element method. The results meet the design requirements of the motor and ensure the reliability of the wheel-side motor. The lightweight design of the wheel-side motor provides an idea for further reducing the weight of the motor.