In order to improve the vibration performance of a vehicle, the twoaxis interconnected hydropneumatic suspension system on same side was proposed. The mathematic model of the hydropneumatic suspension system was built based on its structures and working principles. The characteristics of rigid force and damping force for the suspension system were investigated, the connectivity of the suspension system was analyzed, and the effects of system parameters on the performance were studied. The response mechanism of excitation for the suspension system was studied. The results show that the vibration stability of the twoaxis interconnected hydropneumatic suspension system on same side is better than normal hydropneumatic suspension system, and can recovery equilibrium state faster, so its more conducive to rapid through complex pavements. The damping force is unconnected and determined by many factors. The frequency of the excitation mainly influences the damping force and the phase difference mainly affects the rigid force of the suspension.