We using PIAnO proposed and validated a design process that can optimize the weight of the SUV BIW model while meeting the requirements of stiffness,mode and safety.The BIW weight reduction optimization design is obtained by sensitivity analysis and approximation optimization.First,splitting the BIW model into multiple areas according to the influencing characteristics about the responses.The thickness and the materials of the parts are taken as the design variables for each response.Here,selecting 49 parts thickness and materials parameters as variable for optimization.Next,taking sensitivity analysis and approximation optimization for stiffness and mode case,and sensitivity analysis only for crash safety.