The traditional approach of longitudinal cutting in suspension system simplification introduces redundant degrees of freedom, leading to increased system errors. This study focused on a seven degrees of freedom (7DOF) car model and constructed a suspension system topology model based on an across-cutting approach. To emulate road surface excitation, the filtered white noise method was employed. MATLAB/Simulink was used to create simulation models for the across-cutting, traditional longitudinal cutting and the whole car structure. Comparative analysis of these three topologies was conducted in both the time and frequency domains. Simulation results demonstrated that the performance curve of the across-cutting simplified suspension system closely matched that of the whole car model, validating the accuracy of the proposed across-cutting topology. Furthermore, when compared to traditional longitudinal cutting, the across-cutting simplification method reduced the natural frequency error of body pitch vibration by 25% and decreased the root mean square error of body acceleration by 27%. The suspension topology based on across-cutting more closely resembled the actual car structure, offering a theoretical foundation for enhancing overall ride comfort in automobiles.