Semi-physical simulation bench test is used. By changing parameters of the damping-adjustable hydro-pneumatic suspension system, such as the initial working volume of the nitrogen chamber, rotation angle of the valve core, the frequency and amplitude of sine vibration, the influence curves of dynamic characteristics of root mean square value of acceleration and the vehicle wheel dynamic load of spring mass and unspring mass were obtained. The experimental results show that the vibration acceleration of the spring mass is behind 1/2 cycle than un-spring mass, and the installation of hydro-pneumatic suspension has a significant effect on improving dynamics performance of the off-road vehicle.