Abstract: Based on real cross-sectional images of rock, by tailoring, binary and vector conversion, then importing numerical calculation software, a numerical model was established, the water pressure field and seepage velocity field were analyzed and the permeability coefficient was calculated. From analysis it was found that the water pressure showed the law of progressive decrease from the water inlet to the outlet; The seepage field was uneven, the active channels of seepage were mainly the well connected cracks, and in different boundary conditions, the permeability coefficient of rock mass calculated based on Darcy's law was different.