Abstract: In this paper, the piston rod of new energy vehicle shock absorber is taken as the research object, and the static and dynamic characteristics of its working characteristics are analyzed.Under the premise of ensuring the comprehensive mechanical properties of the piston rod, the lightweight design research is carried out.Six structural parameters such as the diameter of the hollow region of the piston rod were used as design variables to carry out central composite experiment design.The sensitivity analysis of each design variable was carried out, and the response surface model of the hollow piston rod was established according to the obtained data.Multi-objective genetic algorithm was used to complete the optimization design of the hollow piston rod.Compared with the original structure scheme, the overall weight of the hollow piston rod was reduced by 60%, and the lightweight design of the hollow piston rod was realized.This optimization analysis method can shorten the time of R & D and design while ensuring the dynamic and static characteristics of piston rod, and avoid the blindness of selecting design variables.It is of great significance to the research of lightweight optimization design of automobile parts.