Based on discrete element method(DEM),the segregation of granular flow on an inclined plane was numerically investigated in order to investigate its mechanism.The flows with the granular mixture with the same density and different sizes and the mixture with the same size and different densities were simulated respectively on an inclined plane with different roughness.Numerical results show that the granular flow with the same density and different sizes segregates obviously and it gets more obviously when the roughness of the plane is larger.However,the flow with the same size but different densities mixes well in the current study.