Abstract: Grouting is an effective means to prevent and control water damage under moving water condition. In order to master the diffusion law of slurry in fracture under moving water condition, the numerical calculation method of multiphase flow phase field method was adopted. In the process of moving water grouting, the flushing effect of moving water on slurry, the slurry - water interface and the distribution characteristics of velocity field were solved, and the effects of fissure angle and moving water velocity on slurry diffusion were studied. The results show that: moving water mainly scour the slurry along both sides of the diffusion body, separating part of the slurry from the main body and causing the slurry loss; the slurry-water interface also has obvious time-varying due to the time-varying viscosity of the slurry-water interface; under the influence of moving water scouring, the velocity mutation phenomenon exists in the downstream flow zone on both sides and the lower side of the diffusion main body; the increase of fracture angle and velocity of moving water will enhance the scour effect of moving water on slurry, and then affect the diffusion of slurry. The conclusion can provide technical reference for the theory and engineering practice of moving water grouting.