This paper is concerned with optimum design of a center-pillar assembly induced by the high-speed side impact of the vehicle using advanced high strength steels(AHSS). Nowadays steel industries promote ULSAB-AVC project for applying AHSSs as an alternative to improve crash characteristic and fuel efficiency because it is superior comparing with conventional steels in the aspect of strength. In order to simulate deformation behavior of the center-pillar assembly, a simplified finite element model is adopted and parts of that are subdivided employing tailor-welded blanks(TWB) in order to control the deformation shape of the center-pillar assembly. The thickness of each part which constitutes the simplified model is selected as a design parameter. Initial design is a result of thickness optimization using conventional steels and factorial design is carried out aimed at the application and configuration of AHSSs to a simplified side impact analysis because it is impossible to considering all combinations of parts. In optimization of the deformation shape of the center-pillar, S-shaped deformation is targeted to guarantee reduction of the injury level of a driver dummy in the crash test. The objective function is constructed so as to minimize the weight and lead to a S-mode deformation shape. After the optimization, the vehicle weight is highly reduced comparing with the case of using conventional steels. The result shows that AHSSs can be utilized effectively for the minimization of the vehicle weight and the induction of S-shaped deformation.