Abstract: A tailor-welded blank technology was used to perform the integrated design of structure and material for B-pillar. To meet the collision performance, the intrusion displacement and invasion speed of B-pillar were controlled under lightweight design. Based on the C-NCAP, a finite element model of the side collision system was built and verified. A parametric model of B-pillar was built based on the mesh morphing technology. On the basis, three structural design variables and two material type design variables were defined. Then, setting the mass, maximum intrusion displacement and maximum invasion speed of the middle of B-pillar as the multi-objectives, the maximum intrusion displacement and maximum invasion speed of the upper and lower of B-pillar as constrains, the radial basis function (RBF) surrogate model and non-dominated sorting genetic algorithm (NSGA-Ⅱ) were applied to perform the multi-objective optimization design of B-pillar. The Pareto front was obtained and some compromise solutions were discussed to verify the effectiveness of structure design of B-pillar.