In order to study the mixing process and mechanism of horizontal intensive mixer and improve the mixing efficiency, DEM software is used to study the mixing uniformity and efficiency of intensive mixer. Firstly, a numerical simulation model of the horizontal intensive mixer is established; and then the influence of 4 parameters, such as the particle size of the mixed raw material, the filling rate, the water content, and the rotor components on the material mixing time, the mixing uniformity and the wear of the rotor components, are studied and analyzed; finally, the validity of the numerical simulation results is verified by orthogonal tests. The results show that the water content has a significant effect on the mixing degree; the best mixing degree in the cylinder is achieved at 10% filling rate, 55 r/min speed, 3 J/m² surface energy, 8.5 mm particle size of iron-containing raw material and solvent, and 6.5 mm particle size of fuel.