Abstract: This paper studies the lithology, physical properties, oil-beating and seeping characteristics of lowpermeability reservoirs by using the core data from Daqing Xingshugang oilfield. Based on the starting pressure gradients measured from the cores with different permeabilities, there exists a good correlation between starting pressure gradients and permeabilities. The order of magnitude of the changing rate of different reservoir starting pressure gradients is different. Thus, a new classification method of low-permeability reservoirs is set up. Using this new classification method, the upper limit of low-permeability reservoirs is redefined and the low-permeability reservoirs are classified into three types.