In light of damping valve cooling and control response lag, this paper proposes a novel hydro-pneumatic spring to improve damping characteristics by using an external electro-hydraulic proportional relief valve. The dynamic model of the hydro pneumatic suspension was established using AMEsim software and verified by the bench test. Based on this model, the effect of the relative parameters on suspension stiffness and damping was analyzed. The random road excitation response from the fuzzy logic controller combined with the suspension model was compared with that from the passive hydro-pneumatic suspension. The simulation results indicate better performance of the fuzzy logic controller and verify the practicability of the electro-hydraulic proportional relief valve.