In this paper ANSYS Workbench platform is used for static and dynamic finite element analysis of the battery enclosure, and the weak position of the box structure is obtained, then emboss structure is designed on the surface of the upper cover for local reinforcement. Based on the topography optimization technique of the Optistruct software, the geometric parameters and plane layout of the enclosure structure are obtained by optimizing the local stiffness of the upper cover , final the three-dimensional model of the optimized upper cover is established. It is verified that the maximum deformation of the upper cover is reduced by 71.73% and the first natural frequency has reached the design requirement, the stiffness of the upper cover is improved significantly, which lays the foundation for further research on the actural structure of battery pack enclosure.