Based on the unique advantage of the extended finite element method in solving the discontinuous problem, the hydraulic splitting load was simulated by water pressure on the crack surface to solve the nonlinear and moving boundary problems of crack propagation. According to a proposed concrete gravity dam, the cohesive crack propagation model was established by ABAQUS to simulate hydraulic fracturing, and the upstream overload hydrostatic pressure was used to simulate the action of water pressure. Then, the effects of crack length, angle and water pressure on crack propagation were studied. The results show that the crack initiation direction is basically consistent with the preset crack direction under the same initial crack angle and water pressure. When the angle between the preset crack and the horizontal direction is 45 degrees, the crack propagation depth is the shallowest. In addition, with the increase of water pressure on the crack surface, the pre-set cracks on the dam heel gradually propagate to the dam base. With the increase of the preset crack length of the dam fracture section, the stress around the preset crack increases gradually, and the maximum opening displacement of the dam crest and the main crack also increases. Finally, a main crack is formed and continues to expand downstream of the dam foundation, the bearing capacity of the structure gradually decreases.