Abstract: In the reconstruction of pumped-storage hydropower in the mine, the change of seepage field caused by the excavation of the underground reservoir leads to the readjustment of the stress field, which will easily cause the instability and deformation of the surrounding rock. Therefore, the stability of surrounding rock has become the key to the reconstruction of the underground space in Shidangshan Copper Mine. Based on this, a mathematical model of groundwater seepage and geostress that takes into account the fluid-soild coupling is established, and a numerical model is constructed by using the COMSOL Multiphysics software and finite-element method, and the three-dimensional geological model and two-dimensional sectional model are combined to carry out the stability analysis of the surrounding rocks in underground reservoir of the proposed pumped-storage hydropower in Shidangshan. The results show that the underground seepage field changes after the excavation of the underground reservoir, the direction of groundwater seepage changes, and the water level is funnel-shaped. The pore water pressure near and on top of the underground reservoir decreases, and the high pore pressure area is distributed at the bottom of the model on both sides of the underground reservoir. Compared with the case without considering the fluid-solid coupling, the stress, displacement and plastic zone of the surrounding rock are changed after considering the fluid-solid coupling, the maximum equivalent force decreased by 0.9 MPa, and the minimum equivalent force is increased by 0.3 MPa. The equivalent stress on both sides of the cavern shows a decreasing trend, and the boundary cavern is more affected by pore water pressure. The deformation of the surrounding rock of the whole cavern is decreased, and the deformation of the boundary cavern is larger than that of the inner cavern. The fluid-solid coupling reduce the distribution of the plastic zone to a certain extent. Further based on the numerical model of fluid-solid coupling, the stress distribution state and stability of the surrounding rock under filling and releasing water conditions of the underground reservoir are designed. Simulation results show that the designed three conditions of hydrostatic pressure exerted on the surrounding rock, pore water pressure changes caused by water level changes and the stability of the softening effect caused by the change is small, the softening effect to a certain extent weaken the stability of the surrounding rock, in the underground reservoir support need to pay attention to the lining of the cave, the stability of the surrounding rock under the designed conditions of the lower reservoir can still be guaranteed. In summary, numerical simulation is used to evaluate the stability of the surrounding rocks of the underground reservoir in the mine reconstruction pumped-storage hydropower to provide data support and ensure the safety of the project.