In order to further understand the seepage characteristics and differences of oil displacement agent in artificial cores and natural cores，pore structure of the artificial cores and natural cores and its effect on the seepage characteristics of oil displacement agent were tested in Sazhong reservoirs of Daqing oilfield by means of test，chemical analysis and physical simulation theoretically guided by polymer materials science，physical chemistry and reservoir engineering. The results show that the natural cores have the features of more complicated pore structure，poorer sorting system，worse connectivity，stronger heterogeneity and different pore-throat size compared with the artificial cores. The main difference of pore structure between low permeability and high permeability artificial cores is the pore-throat radius. When the flow of polymer solution，polymer/surfactant binary compound system，strong base ternary compound system and weak base ternary compound system gets stable，the average ratio of resistance coefficient of the natural cores to that of the artificial cores is 1.69，1.73，1.78 and 1.65 respectively，which indicates that the natural cores have larger hold-up volume of oil displacement agent，greater seepage resistance and higher injection pressure but the pressure value still tends to be stable and plugging will not occur in the natural cores compared with the artificial cores.