Water inrush disasters in geotechnical engineering are mainly caused by seepage in fractures, and curtain grouting is the most common method to block water flow. To ensure the effectiveness of the water blocking curtain, it is necessary to study the diffusion pattern of the slurry. In this study, by means of laboratory experiments and theoretical deductions, the grout diffusion morphology in fractures with the slurry-rock stress coupling effect is revealed, and the corresponding theoretical model is established. First, based on the failure of a water curtain in a hydropower project in Yunnan Province, a four-level four-factor orthogonal table was set up, grouting experiments were conducted by using the self-developed fracture grouting device, and the relationship between the main influencing factors and fracture deformation and grout diffusion distance was revealed by variance analysis. Then, based on the Bingham fluid constitutive model, the fracture deformation equation and the grouting model with flowing water, a new fracture grouting model considering the coupling effect of slurry-rock stress was established. Finally, based on the calculations and experiments, the morphology of slurry diffusion is described, thereby proving the validity of the new model.