Abstract: It is of great significance to uniformly describe the solid-liquid two-phase flow with different particle volume fractions. The unified two-phase flow model that takes into account the granular rheology in different flow regimes, the interaction between solid and fluid phases and the turbulent flow effect, is adopted to investigate dilute and dense granular flows in this paper. Compared with the experimental data, the numerical results demonstrate that the two-phase flow model can well describe the flow process of dilute and dense granular flows with different particle sizes. The simulation results show that the interaction between dilute particles and the ambient fluid varies with the particle size, and fine particles are more likely to be suspended in the ambient fluid and transported longer due to the weaker sedimentation processes. The fluid eddy viscosity plays an important role in the development of fluid vortexes, and the fluid phase with the turbulence model tends to move forward and further facilitates the progress of dilute particles. The numerical results in dense granular flows show that the drag force near the deposit surface is much larger, and causes fine particles to move outward in a long period, but mainly retards the movement of coarse particles. The dynamic pressure effect in fine dense particles is more noticeable, and the positive dynamic pressure accelerates the flow of initial granular fronts, while the negative dynamic pressure modifies the granular deposit topography.