Abstract: During the seepage of the shale gas, its effect is due to the large Knudson number, which makes the gas molecules slip from the solid surface. Based on the REV (representative elementary volume) scale lattice Boltzmann method, the flow of the shale gas is simulated with consideration of the slippage effect. With the scanning electron microscope image, a physical model with organic rock, nonorganic rock and natural fractures is taken, and then the shale gas flow in the model is simulated. The simulated results indicate that the shale gas mainly flows in the natural fractures. However, the shale gas also flows slowly in the organic and nonorganic rocks, and the velocity in the organic rocks is larger than that in the nonorganic rocks. The influence of the reservoir pressure on the shale gas seepage is also studied by varying the reservoir pressure. It is indicated that with the decrease of the reservoir pressure, the Knudson number increases and the slippage effect intensifies, thus the velocity and the permeability of the whole fluid field increase.