Based　on　global　initiatives　such　as　the　clean　energy　transition　and　the　development　of　renewable　energy,　the　pumped　storage　power　station　has　become　a　new　and　significant　way　of　energy　storage　and　regulation,　and　its　construction　environment　is　more　complex　than　that　of　a　traditional　reservoir.　In　particular,　the　stability　of　the　rock　strata　in　the　underground　reservoirs　is　affected　by　the　seepage　pressure　and　rock　stress,　which　presents　some　challenges　in　achieving　engineering　safety　and　stability.　Using　the　advantages　of　the　numerical　simulation　method　in　dealing　deal　with　nonlinear　problems　in　engineering　stability,　in　this　study,　the　stability　of　the　underground　reservoir　of　the　Shidangshan　(SDS)　pumped　storage　power　station　was　numerically　calculated　and　quantitatively　analyzed　based　on　fluid-structure　coupling　theory,　providing　an　important　reference　for　the　safe　operation　andmanagement　of　the　underground　reservoir.　First,　using　the　COMSOL　software,　a　suitablemechanicalmodel　was　created　in　accordance　with　the　geological　structure　and　project　characteristics　of　the　underground　reservoir.　Next,　the　characteristics　of　the　stress　field,　displacement　field,　and　seepage　field　after　excavation　of　the　underground　reservoir　were　simulated　in　light　of　the　seepage　effect　of　groundwater　on　the　nearby　rock　of　the　underground　reservoir.　Finally,　based　on　the　construction　specifications　andMolar-Coulomb　criterion,　a　thorough　evaluation　of　the　stability　of　the　underground　reservoir　was　performed　through　simulation　of　the　filling　and　discharge　conditions　and　anti-seepage　strengthening　measures.　The　findings　demonstrate　that　the　numerical　simulation　results　have　a　certain　level　of　reliability　and　are　in　accordance　with　the　stress　measured　in　the　project　area.　The　underground　reservoir　excavation　resulted　in　a　maximum　displacement　value　of　the　rock　mass　around　the　caverns　of　3.56　mm　in　a　typical　section,　and　the　safety　coefficient　of　the　parts,　as　determined　using　the　Molar-Coulomb　criterion,　was　higher　than　1,　indicating　that　the　project　as　a　whole　is　in　a　stable　state.　©　2024　Tech　Science　Press.　All　rights　reserved.