Abstract: The structure characteristic and working principle of the hydro-pneumatic buffer for ship were summarized. Based on the fundamental dynamics knowledge, the mathematics model between shock input and shock output of hydro-pneumatic buffer was established. Through numerical simulation of Matlab, the relation between shock resistance of hydro-pneumatic buffer and influence parameters, such as orifice in compression stroke, orifice in expansion stroke, inner diameter of oil chamber, and the height of the gas chamber was established.