Dam seismic safety is a key technical problem related to national water resources safety, and even social and public safety. Seismic safety evaluation and dynamic interaction analysis of dams are important in practical engineering. In this research, an overall analysis model of gravity dams considering dam-foundation-reservoir interaction was established, the reservoir was simulated by acoustic elements, and the feasibility of this simulation method was verified by several examples. Then, the crack propagation process of the dam was simulated by the extended finite element method, and the contact model considering the opening and closing of the crack surface was established. Taking Jin'anqiao RCC gravity dam as an example, the gravity dam-foundation-reservoir-dynamic interaction model was established. The effects of the additional mass method, the fluid-structure coupling model without considering the compressibility of the reservoir and the compressibility of the reservoir water on the seismic cracking process of the gravity dam were discussed. The overload potential of the gravity dam with cracks and the influence of the initial crack position on the crack propagation were analyzed. The results show that the additional mass method and fluid-structure coupling model without considering the compressibility of reservoir water exaggerate the earthquake action, and a longer crack propagation and larger crack can be observed. With the increasing of the seismic peak acceleration, the initial position of the downward deflection of the crack propagation path of the gravity dam continues to extend to the interior of the dam, and the dam will produce long cracks under the seismic load with the seismic load of 1.3 times of the design seismic acceleration. The initial crack at the slope break point propagates more obviously under seismic load.