To improve the lightweight effect and safety performance of a commercial vehicle battery pack， the modal， impact， collision simulation and extrusion analysis of the original aluminum battery pack lower shell were carried out according to the requirements of the battery pack safety test in the national standard， and it was found that there was a design defect of insufficient anti extrusion ability. Then， the structure was redesigned according to the shortcomings， and a new lightweight battery pack with multi material fusion was obtained. Meanwhile， the section of aluminum profile for battery pack frame structure is optimized， and a reasonable section scheme of aluminum profile is obtained， which can not only meet the safety requirements of battery pack structure， but also have the feasibility of low-cost and efficient production. Finally， based on the finite element analysis of different battery pack frame structure schemes， the optimal battery pack frame structure scheme meeting the production requirements of the factory is obtained. The results of the physical extrusion test show that after lightweight structure design and optimization， the weight of the battery pack is significantly reduced， and the safety performance meets the requirements of the national standard. Compared with the original design scheme， the lightweight effect of the optimized frame battery pack scheme is 12.3%.