Abstract: The top-down design method of a mobile radar antenna array is proposed in this paper. The classical mechanics is used to solve the maximum stress and deformation of the antenna array in static working condition. Then the mathematical model is built, taking the maximum stress and deformation as the optimization constraint conditions and the mass of the antenna array as the optimization objective. The first optimization design is carried out using genetic algorithm and the initial structure parameters are obtained. A parameterized finite element model is further established using APDL of ANSYS system. The antenna structure parameters are obtained after the second optimization, with both the static condition and dynamic condition considered. Top-down design is conducted in the design of a type of mobile radar, and the optimization result is compared with the existing result of this radar. It shows that the top-down method is reasonable and the lightweight effect is obvious.