Abstract: The development height of the water conducting fracture zone is one of the most important parameters for coal mining under water bodies. Coal seam mining can easily induce fault activation, leading to an increase in the development height of the water conducting fracture zone. In response to the difficulty in determining the height of water conducting fracture zones caused by faults, numerical simulations are used to study the distribution of plastic zones, stress, and displacement changes in overlying rock during mining. The results show that under the influence of faults, the plastic zone of the overlying rock in the mining face significantly increases, stress concentration near the fault increases, and the subsidence of the rock layer increases. Compared with the expected results of the empirical formula without faults, the development height of the water conducting fracture zone without faults is 22.17-36.84 m, and the development height of the water conducting fracture zone without faults is 1.2-2.1 times that of the development height without faults. Under the influence of mining, fault cutting destroys the integrity of rock layers, affects the propagation of mining stress, and causes stress concentration near the fault, leading to fault activation and the development of water conducting fracture zones. The research results can provide theoretical basis and application reference for coal mining under similar conditions in water bodies.