High concrete gravity dams operating perennially under the condition of high water pressure are prone to hydraulic fracturing failure. In this study, the hydraulic fracturing characteristics of the dam heel crack in a high concrete gravity dam were analyzed, the influence of water pressure inside the crack on the expansion of hydraulic fracturing crack was studied, and the stability of hydraulic fracturing crack and anti-sliding stability of dam foundation surface were discussed. The results show that if the initial crack is 3.0 m away from the dam heel and the depth of the crack is 2.0 m,the ultimate bearing capacity of the dam body under the water pressure in the crack decreases by 17.6% compared with that without considering water pressure inside the crack. If the initial horizontal crack depth is 2. 0 m and the distance from the crack to the dam heel is less than 5. 0 m, the crack of the dam body is in the tension shear fracture mode. If the initial horizontal crack is located at the dam heel position, the safety coefficient of anti-sliding stability of dam foundation surface in the joint under the action of water pressure decreases obviously, with a decreasing rate of 8 times compared to the case without considering the water pressure inside the crack. The effect of water pressure inside the crack is unfavorable to the crack stability and anti-sliding stability for gravity dam heel.