Abstract: In recent years the lightweight design of antenna has been widely concerned. With the rapid development of optimization theory and simulation technology, the lightweight design of antenna based on topology optimization has become an important research direction. In this paper, an all-metal Vivaldi antenna is taken as the research object. The lightweight design of the antenna element is carried out based on the basic theory of topology optimization and by finite element simulation. The simulation results show that the total weight of the antenna array has been reduced by nearly 15% under the premise of satisfying the dynamic characteristics and radiation characteristics, which meets the predetermined requirements. Therefore, it is an effective lightweight design method.