Abstract: The cracks in the heel of gravity dam usually bear the action of high water head during the operation of the dam, which is prone to hydraulic fracturing failure. In this paper, the crack hydraulic fracturing coupling numerical model of gravity dam under the framework of extended finite element method is established, and the crack propagation process of gravity dam heel under the coupling of hydraulic fracturing is simulated by extended finite element method. The calculation results show that the heel of the gravity dam initially gradually extends to the dam base, and the crack propagation direction is towards the downstream. The crack angle without hydraulic fracturing is larger than that under hydraulic fracturing, and the crack angle without hydraulic fracturing coupling is smaller than that under hydraulic fracturing coupling. Before the crack propagation in the heel of gravity dam, the water pressure in the crack is basically the same as the boundary water pressure. When the crack begins to expand, the water pressure in the crack will drop, and then the crack opening width will continue to increase, and the water pressure in the crack will become the boundary full head. Hydraulic fracturing of cracks leads to the increase of type I stress intensity factor at the crack tip and reduces the stability of cracks in gravity dam. The research results provide an important theoretical basis for the hydraulic fracturing prevention of cracks in the heel of gravity dam.