The soil and rock mixture is widely spread in the world， which is much different from homogeneous and continuous soil, it is hard to get the permeability of the soil and rock mixture by theories, and it is also hard to get that from the large lab test as the difficulty in sampling. The particle flow code (PFC) method is used to study the permeability character influenced by large rock particles. The result shows that the seepage of the soil and rock mixture obeys the linearity of Darcy’s law in low fluid velocity, but the large particles influence the local pore pressure evidently. The permeability increases while the ratio of rock to soil increase first, and decreases while the ratio enlarge to 0.5, then increases after the ratio enlarge to 0.7. The large rock particles jam the fluid path, but decrease the length of the pipe, the permeability is influenced by the two effects.