This research deals with the static and dynamic methematical models and numerical simulations of ring gap-damping high pressure relief valve. The linear differential equations set is solved using boundary layer calibration method of strange perturbation theory. Through theoretical analysis and test verification, the paper gives the causes for the pressure pulsation in the fore chamber of the pilat valve and the additional flow. The static and dynamic characteristics of two types of slide valves, i.e. with and without spring at the valve end, are analyzed and compared, indicating that the former is superior to the latter in performances, thus forming the theoretical and experimental basis for application of ring gap-damping high pressure relief valve. The research also examines the influences of the valve's structural parameters on its performances. On the basis of this, valve design is modified leading to excellent static and dynamic performances and good application effectiveness.