Vehicle handling stability is an important part of the vehicle performance, usually in the vehicle suspension and subframe system often subframe as a rigid connection for research, however, the front subframe will be elastic deformation in the actual driving process, the front subframe of a certain model of flexible processing, the establishment of rigid-flexible coupling vehicle model to study the handling stability of the whole vehicle is of great significance. Based on this model, the lateral dynamics of the whole vehicle is analyzed, the three-degree-of-freedom vehicle kinematics equations are derived, and the vehicle kinematics simulation is conducted for comparative analysis to study the influence of the front subframe flexibility on the KC characteristics of the suspension system and the transient handling stability of the whole vehicle. The NSGA-II algorithm is used for the optimal design of suspension parameters to optimize the transient handling stability of the whole vehicle.The optimization results show that at 0.5 HZ, the yaw rate gain relative to the steering wheel angle is reduced by 8%, the body roll angle relative to the lateral acceleration gain is reduced by 1.1%, and the lateral acceleration delay time relative to the steering wheel angle is reduced by 10.5%.