To reduce the weight of the electric scooter frame, magnesium alloy is used to replace the steel. At the same time, the frame structure and tube thickness are redesigned by using topology optimization and size optimization respectively. In addition, static analysis and mode analysis of the frame are carried out to realize the application capability and dynamic capability. Compared with the original steel frame, mass of the magnesium alloy frame after optimization has been reduced by 60%, and the natural frequency has been improved greatly. The results show that the strength and the rigidity of the new structure can meet the designed demand.