By choosing a car white body as reference,the white body finite element model is established. Being based on torsion condition set constraints,white body weight was chosen as the objective function of the parts thickness as the design variables. The value of the sensitivity of various parts was calculated by using Nastran. The sensitivity value of the parts was evaluated by introducing a concept of average absolute sensitivity and the absolute sensitivity. The parts thickness thinning processing and validation were optimized by iterative calculation optimization solution. Finally the quality white body reduced at 3. 73% under the premise of no more than 5%.