To study the effect of polyurethane grouting on the crack repair performance of cement stabilized crushed stone, a microscopic model of cement stabilized crushed stone was established by the discrete element method (DEM) in this paper. SCB fracture simulation tests were conducted on specimens with different initial notch-to-depth ratios to obtain load?displacement curves, and sensitivity analysis of microscopic parameters was performed. Then, by comparing microscopic characteristics such as crack propagation paths, crack types, and particle displacements before and after grouting, the repair effect of polyurethane grouting materials was evaluated. The results indicate that the grouting filler significantly enhances the overall stress uniformity of the specimens, expands the tension zone, and disperses internal particle displacements; after grouting, the crack propagation paths of the specimens are similar to those before grouting, but the polyurethane grouting material effectively suppresses crack initiation from the pre-cut notch; cracks mainly propagate along the aggregate?mortar interface at the bottom central axis and the mortar interface at the bottom of the loading plate; crack propagation undergoes three stages: slow accumulation, rapid propagation, and stabilization; the grouting filler significantly improves the crack resistance of the specimens, delays the time of crack generation, and suppresses the rapid propagation of cracks, among which the crack resistance is optimal when the notch-to-depth ratio is 0.4R (R is the specimen radius); tensile stress is the driving force for crack propagation, and the aggregate-mortar interface and the interior of the mortar are the main weak failure interfaces; polyurethane grouting can significantly improve the crack resistance of cement stabilized crushed stone, enhance the structural integrity of the specimens, and improve stress distribution.