Abstract: In order to study the effect of parameter variation on the stiffness and damping characteristics of interconnected hydro-penumatic suspension, a non-linear mathematical model of interconnected hydro-penumatic suspension was formulated considering the compressibility of fluid and the motion friction. A test bed was constructed and a simulation model of interconnected hydro-penumatic suspension was established. The simulation results were compared with experiment results and theory results. The error was within 10%. Besides, the effects of initial inflation pressure, excitation frequency, and phase difference between the right and left hydraulic cylinders on interconnected hydro-penumatic suspension were also investigated based on the mathematical model. The results indicated that the bigger the initial inflation volume was, the smaller the stiffness became. The bigger the excitation frequency and phase difference were, the bigger the stiffness and damping characteristics became. The initial inflation pressure can hardly affect the characteristics.