Abstract: With the underground engineering projects such as pumped storage power stations under complex hydrogeological conditions, grouting technology in fractured rock masses has become a key measure to ensure anti-seepage safety. This paper systematically reviews the current research status of grouting diffusion mechanisms in fractured rock masses under flowing water conditions, with a focus on theoretical models including permeation grouting, compaction grouting, fracture-splitting grouting, and fracture grouting, as well as their engineering applications. Studies have shown that the rheological properties of the grout, fracture roughness, flowing water velocity, and grouting pressure are the main factors influencing grout diffusion behavior. Current research is largely based on simplified fracture models, and there remains a lack of in-depth understanding of the grouting process in complex fracture networks and under multi-field coupling conditions. Numerical simulations and experimental studies have made certain progress in revealing grout diffusion patterns, but further integration with discrete fracture network (DFN) models and multi-physical field coupling methods is needed to enhance model authenticity and prediction accuracy. Future research should emphasize the synergistic innovation of materials, mechanisms, and processes to advance grouting technology from empirical practice to a more scientific and intelligent direction, providing theoretical support and technical assurance for engineering anti-seepage under high water pressure and high permeability.