Abstract: Faced with the poor reliability of hydro-pneumatic suspension installed on off-road vehicles,a composite suspension is designed,where the elastic force is supplied by both the helix spring and hydro-pneumatic suspensions.The helix spring and the hydro-pneumatic suspension are used in parallel.The method for composite suspension stiffness matching is proposed based on its use on an off-road vehicle.The working pressure,load characteristics and stiffness characteristics of the composite suspension system are compared with that of the hydro-pneumatic suspension,and the vehicle body vertical acceleration,suspension travel and dynamic load of wheels are compared by simulation.The result showed that the composite suspension is more suitable for using on off-road vehicles than hydro-pneumatic suspension,the composite suspension can reduce the work pressure,improve the reliability,and thus enhancing the riding comfort.