The numerical simulation of soil-rock mixtures(S/RM) shear test was successfully performed using the particle flow theory based on particle flow code (PFC), by creating irregular clumps, constant normal stress and rock content in shearing surface. Based on the clump of PFC with different stone content, different normal stress of S/RM direct shear test simulation were elaborately discussed. The reliability of the simulation method was verified by comparing calculation results and in-situ shear test. The main research results indicate that with the increase of rock content, the shear stress and the peak shear stress increase, while the shear displacement at the peak shear stress decreases. S/RM samples exhibit shear dilatation characteristics at low normal stress and tend to transform from shear contraction to dilatation at higher stress, with pressure shear failure characteristics. In the near shear plane distributing the irregular rock clump, the shear appeares in the process of extrusion sliding and rolling shear failure surface grows concave and convex. With shear displacement increasing, the shear stress and strain energy  fluctuate and grow gentle. The peak shear stress obtained from the numerical calculation is higher than that of the insitu test. The calculated peak shear stress can be decreased effectively by reducing the particle radius.