Abstract: In this paper,the methods of geometric leveling,spheric harmonic function and hydrostatic leveling used for calculating the mechanism of off-shore sea surface topography are presented,where the hydrostatic leveling method is mainly mentioned.The paper also pointed out that the isostatic effect and non-isostatic effect of atmospheric pressure must be considered when the Chinese off-shore sea surface topography is computed by using the hydrologic data.With the quantitative analysis of the effects on Chinese off-shore sea surface topography caused by the factors of hydrology and atmospheric pressure,and the north equatorial current(Kuroshio)in pacific ocean as well,some useful conclusions have been obtained.