Abstract: According to the SA beisandong block s II reservoir sandstone rock thin section, high pressure mercury, scanning electron microscopy (SEM) data test data analysis and fine characterization of the reservoir in the study area reservoir microscopic characteristics. Research shows that the study area s II reservoir multi hole infiltration, permeability change is big, strong homogeneous reservoir, pore connectivity, more small pore throat, suggesting that there were potential velocity sensitivity and alkali sensitivity of reservoir.