The body in white is an important part of the automobile, and many automobile manufacturers have taken the body in white as one of the important research directions. If lightweight design can be applied to the white body, it can achieve the purpose of energy saving and emission reduction. A car body in white was taken as the research object, and the adaptive response surface method was used to optimize and solve the car body in white. Firstly, the modal, stiffness and strength of the body in white were obtained by the finite element method, and 15 sheet metal parts were selected as variables by modal and stiffness sensitivity analysis. The 15-factor 3-level experiment was designed by the Taguchi experiment, and the response surface was created according to Taguchi experiment data. Then, the least square regression and moving least square method were used to fit the response surface, the adaptive response surface method was used to optimize the solution, and the simulation experiment was compared. The results show that the proposed method can reduce the weight of the body in white by 18.924 kg, which is 4.736 9%, and realize the lightweight requirements of the body in white under the conditions of stiffness and strength.