Based on the characteristics of high strength and modulus of carbon fiber-reinforced composite (CFRP), in this article, the CFRP material was used to replace the steel material of the automobile’s B-pillar inner and outer plates, and the three-stage optimization design of the lamination structure was carried out. Firstly, this article used the principle of equal stiffness replacement to determine the thickness of the carbon fiber B-pillar inner and outer plates, and the structural design of the replaced B-pillar was also carried out. Secondly, on the basis of the vehicle collision model, the B-pillar subsystem model was extracted, and the material replacement and collision simulation were carried out. Thirdly, the free-size optimization, size optimization, and lamination sequence optimization of the CFRP B-pillar were performed to get the best ply structure; the objective of optimization was to minimize the carbon fiber B-pillar inner and outer plates mass, and the constraint conditions of optimization were the intrusion amount and intrusion speed of the B-pillar loading points. Finally, the optimization results of carbon fiber B-pillar were verified by simulation. The research showed that, under the requirements of rigid strength and technology, the mass of the B-pillar after the replacement of equal stiffness somewhat decreased, the lightweight rate reached 55%, and it had better energy absorption and impact resistance. After optimization, the mass of the B-pillar was further reduced, the lightweight rate reached 63.5%, and the energy absorption and impact resistance were further improved.
