Cement slurry grouting method is widely used in stabilization of tunnel construction with soft and weak rocks, with an evaluation of the grouting effect by the slurry diffusion range. A joint DXF file can be created by copying and importing it into COMSOL software, with the Barton roughness standard curve adopted. A four factor three-level orthogonal experimental scheme is to be designed based on the grouting diffusion distance, including joint roughness, grouting pressure,slurry viscosity, and joint openness, followed by an analysis of the influence of these four factors on the grouting diffusion. The results indicate that an increase in grouting pressure and joint openness can enhance the slurry diffusion range, while an increase in viscosity presents the opposite effect. An increase in joint roughness increases the corner effect of the slurry diffusion, leading to a decrease in diffusion distance. By using range analysis and variance analysis, it is found that the four factors that follow the order from the greatest to the least slurry diffusion effect are slurry viscosity, grouting pressure, joint openness, and roughness, with an additional proposal of the combination level of the four factors at the maximum slurry diffusion distance.