Abstract: Natural and artificial porous media are generally campased of heterogeneous materials more or less randomly packed ug.Complicated in geometry and difficult for mathematical presentation,it is impossible to make a completo description of the flow behavior within the parous media.We have to use the statistical concept in order to examine the effect of flow behavior on the parameters of the characteristic pore structure.For the purpose of finding out the laws if changes of such parameters,sandstone samples from oil fields in Lamadian,Sartu and Xingshugang were analysed with mercury porometer and scanning electron microscope.Waterdrive experiments with natural and artificial cores were also conducted for studying the relation of pore-structure parameters with water drive efficiency and relative permeability curves.Results thus obtained are used in setting up quantitative indices for further studies of the mechanism of water drive of oil.Changes in the structure of porous rocks after long wash by water are also studied.