Abstract: Aiming at the crashworthiness optimal problem of autobody structures during low-speed frontal crash, the crash box is chosen as a subject to be analyzed and designed to optimize the vehicle frontal crashworthiness capacity. The secondary regressive orthogonal-composite design (ROCD) and least-square method are employed to construct the response surface models of total mass, energy absorbed value and maximal crash force for investigating the performance of entire structure. Considering the range of actual thickness of the autobody structure and the request of lightweight, the adaptive response surface methodology (RSM) is applied to realize the optimal design. The result demonstrates that the optimal method and process proposed have high accuracy and validity.