Abstract: To address the challenges in simulating grout diffusion and evaluating grouting quality in complex karst fractured rock masses, a 3D fracture model was developed using Latin Hypercube Sampling (LHS) and Discrete Fracture Network (DFN) methods. A multi-hole, double-row grouting model was established in COMSOL, with governing equations for fracture flow and grout transport. The simulation results show that the double-row grouting holes synergistically alter the diffusion pattern, creating a multi-row superposition effect and a "butterfly-wing" shape. The front-row holes induce circumferential flow along karst cave boundaries, while the back-row holes provide pressure compensation to effectively fill dissolution channels, forming a continuous anti-seepage curtain. The relative error between simulated and actual cement usage is 5.58%. This study offers a valuable reference for grouting simulation in complex karst fracture conditions.