The　seismic　behavior　of　deep-water　bridges　across　faults　is　intricate,　influenced　by　intense　earthquake　vibrations,　fault　dislocation,　and　the　often-overlooked　fluid-solid　interaction　between　the　pier　and　surrounding　water　during　seismic　events.　In　this　study,　three-dimensional　finite　element　model　of　a　fault-crossing　deep-water　suspension　bridge　is　established,　and　the　fluid-structure　interaction　between　the　bridge　tower　and　water　is　simulated　by　using　fluid　element　method.　By　employing　an　asymmetric　method,　the　first　20　natural　vibration　characteristics　of　the　bridge　under　different　water　depths　are　determined.　The　ground　motions　of　three　different　magnitudes　under　a　strike-slip　fault　are　synthesized　via　utilizing　a　velocity　pulse　model.　The　influence　of　water　depth　on　structural　seismic　responses　is　defined　through　fluid-solid　coupling　techniques.　The　results　indicate　that:　(1)　The　presence　of　water　reduces　the　natural　vibration　frequency　of　the　suspension　bridge.　However,　at　the　current　maximum　water　depth,　this　effect　is　minimal　on　the　natural　vibration　characteristics　of　the　bridge;　(2)　Conversely,　the　fluid-solid　coupling　amplifies　the　seismic　response　of　the　suspension　bridge＇s　main　tower,　especially　under　full　reservoir　conditions,　where　the　maximum　influence　rate　can　reach　to　29　%;　and　(3)　The　influence　of　fluid-solid　coupling　on　the　main　girder　displacement　during　ground　motion　is　negligible.　These　insights　offer　crucial　perspectives　for　engineering　practices　in　the　design　and　evaluation　of　deep-water　suspension　bridges　under　seismic　events.　©　2025　Institution　of　Structural　Engineers