To　investigate　the　seismic　response　of　the　pile-structure　system　in　inclined　liquefiable　soil　under　horizontal　and　vertical　coupling　excitations,　this　paper　adopted　the　Biot　porous　medium　theory　to　simulate　the　saturated　sand　as　a　solid-liquid　fully　coupled　two-phase　medium.　The　multi-yield　surface　plastic　constitutive　model　was　used　to　simulate　the　seismic　response　of　the　saturated　sand.　The　finite　element　model　of　the　liquefiable　inclined　site-pile　foundation-bridge　structural　system　was　established　using　OpenSees.　The　shaking　table　test　results　were　compared　to　verify　the　reliability　of　the　numerical　model.　On　this　basis,　a　numerical　model　of　pile　foundation-bridge　structural　system　in　typical　liquefiable　soil　was　established,　and　the　seismic　responses　of　the　system　under　horizontal　one-way　and　horizontal　and　vertical　coupling　earthquakes　were　discussed.　The　results　indicate　that　compared　with　the　horizontal　single-direction　seismic　input,　the　pore　water　pressure　of　the　liquefiable　soil　oscillates　prominently　when　the　horizontal　and　vertical　seismic　coupling　acts.　Furthermore,　the　permanent　lateral　displacement　of　the　liquefiable　layer　soil　increases　significantly,　especially　in　the　shallow　and　middle　layers　of　the　saturated　sandy　soil.　Under　the　horizontal　and　vertical　two-way　earthquakes,　the　damage　of　the　pile　is　more　significant,　and　the　vulnerable　positions　are　increased.　The　maximum　curvature　of　the　pile　can　be　increased　by　128%.　The　lateral　displacement　of　the　pile　in　the　middle　of　the　liquefiable　layer　can　be　increased　by　about　30%.　In　addition,　increasing　the　reinforcement　ratio　of　the　pile　can　effectively　curb　the　lateral　displacement　of　soil　and　reduce　the　damage　degree　of　the　pile.　The　vertical　seismic　action　increases　the　inertia　effect　of　the　superstructure,　increases　the　peak　curvature　of　the　pier　bottom　by　about　100%,　and　intensifies　the　damage　degree　of　the　pier　bottom.　Therefore,　the　seismic　design　of　the　pile　foundation　built　in　the　liquefied　lateral　expansion　site　should　consider　the　influence　of　vertical　seismic　action.　©　2023　Science　Press.　All　rights　reserved.