In order to study seepage mechanism of soil, there are some basic assumptions, the soil is saturated, and flow is laminar in the process of seepage. Based on lattice Boltzmann method at the representative elementary volume(REV) scale, the mesoscopic seepage numerical model of soil under pressure is established, considering the effects of macroscopic statistical parameters, i.e. porosity, permeability and effective viscosity coefficient. The D2Q9 model is applied for the discrete velocity direction. In the macroscopic boundary condition, it is impermeable in the left and right sides; and it is controlled by pressure in the upper and lower boundaries, which is decided by setting different density. And the non- equilibrium extrapolation scheme is used in the microscopic boundary. The porous media is set to be fluid in the study region by letting 1.0 and , the corresponding program is compiled to verify the Poiseuille flow. Combined with an example, the influence of porosity, permeability and seepage pressure on the seepage velocity driven by pressure is discussed for soil, and the results of this paper are in good agreement with that calculated by Darcy’s law. Therefore, lattice Boltzmann method at the REV scale could effectively simulate the seepage characteristics of soil, and it provides a new research approach for further study of seepage mechanism.