To optimize vehicle body structure in the conceptual design stage of platform architecture, a new method was proposed. The method includes three stages. In the first stage, considering the real collision load, the multi-model optimization method was used to carry out the global topology optimization under the comprehensive working condition, and the different force transmission paths were interpreted. In the second stage, considering the high and low vehicles of the platform architecture, the body parameter models of different transmission paths were established using SFE CONCEPT. Comparative analysis and optimization were conducted under different power types to determine the form of transmission path of the platform architecture. In the third stage, the approximate model method was adopted to optimize the body section and the equivalent static load method was adopted to optimize the body material thickness, and the optimization scheme was put into different vehicle and power types for verification and optimization, so as to ensure that the body structure was under the target performance bandwidth of platform architecture. In the conceptual design stage of the platform architecture of an automobile enterprise, the proposed method was used to optimize the body structure, and the engineering feasibility of this method was verified.