Abstract: The multi objective optimization design is carried out for the economic benefits and lightweight design requirements of the special hole vehicle body. Setting the main panel thickness as the design variable, the optimization objective is to minimize the mass of the vehicle body and maximize the first-order vertical bending mode under the harsh working conditions; the constraint is that in the event of a change in plate thickness, the deflection of the side beam shall not exceed the standard limit, and the maximum stress shall not exceed the allowable stress. Using the sensitivity analysis, the plate with the greatest impact on the optimization objective is selected as the design variable; the optimization experiments are designed by combining with the Box Behnken design method, and then the response surfaces are generated based on it. The multi-objective genetic algorithm is applied for optimization calculation so as to achieve the main goal of lightweight for special hole vehicles. The results show that quality of the special hole car is reduced by 8.63%, and the modal is improved by 0.83%. Considering the modal information into lightweight design, the results are more reasonable and provide reference for subsequent research on the special hole vehicles.