Abstract: By measuring the porosity and permeability of core samples under different pressures, their relations with pressure are obtained. The results show that porosity and permeability decrease as pressure increases and obey the rule of logarithm function. However, the changing trends are quite different for sandstone samples between different intervals of porosity and permeability. The effect of pore structure on porosity and permeability are confirmed through the capillary pressure curve and nuclear magnetic resonance(NMR) T2 spectrogram of sandstone samples with different grain sizes. The microstructure is the key factor that determines permeability.