Abstract: Grouting diffusion on graded gangue bulk materials is proposed, aiming toobtain the cementing stowing body with good integrity,and high compressive strength. Based on the exponential fluid flow equation and seepage motion equation,the theoretical equation of cylindrical diffusion is established. The slurry diffusion is numerically simulated by COMSOL Multiphysics. It is found that the slurry diffusion radius is positively correlated with the materials porosity,water-cement ratio and grouting pressure. Orthogonal test is designed to study the grouting diffusion of graded gangue bulk materials. The results show that when the compaction strength is 0.8 MPa,the gangue particle size gradation scheme is A₁,and the water-cement ratio is 0.5:1,the strength of cementing body can reach 3.23 MPa in 3 days,6.28 MPa in 21 days,and the average elastic modulus is 19 425.4 MPa in 21 days. The compressive strength of the cementing body increases obviously in the early curing stage,and the integrity and mechanical properties of the filling body are greatly improved. The grouting diffusion law is verified through numerical simulation and grouting diffusion experiment. The results provide reference for optimizing the grouting parameters design of gangue bulk materials.