Abstract: A lot of micro-fractures exist in rock. The wall wettability has a significant impact on the fluid flow due to their small width. Based on the Shan-Chen pseudopotential model, the lattice Boltzmann method is applied to establish the numerical model for studying the seepage properties of a smooth rock micro-fracture. The validity of the proposed model is proved by the simulation of a suspended liquid droplet in vapor and the wall contact angles. The seepage properties of a rock micro-fracture is studied considering the effects of the wall wettability, fracture width, pressure gradient and fluid viscosity. The results show that the hydrophobic wall has an accelerating effect due to the repulsion on the nearby fluid, while the hydrophilic wall has an obstructive effect. In general, the influence of the hydrophobic wall on the micro-fracture seepage is more significant than that of the hydrophilic wall. The effect of wall wettability on the seepage velocity increases with the decrease of the micro-fracture width. The stronger the hydrophilicity/hydrophobicity of wall is, the more significant the influence of fracture width will be. The average seepage velocity increases linearly with the increase of pressure gradient. The stronger the wall hydrophobicity is, the greater the linear slope will be. In addition, the larger kinematic viscosity of fluid is, the greater the flow resistance will be, which results in the decrease of the average flow velocity. In addition, there is an inverse relationship between the average flow velocity and the kinematic viscosity.