In　order　to　study　the　response　law　and　damage　mechanism　of　precast　and　assembled　PC　box　pier　under　the　action　of　bidirectional　earthquakes,　the　box　piers　of　a　highway　bridge　were　taken　as　the　study　background.　Three　PC　box　pier　specimens　(two　precast　and　assembled　piers,　one　integrally-cast　pier)　with　a　scale　of　1:12.5　were　prepared.　The　bidirectional　pseudo-dynamic　loading　tests　were　carried　out　to　analyze　the　failure　modes,　skeleton　curves,　energy　dissipation　and　prestress　variation　law　of　the　three　specimens.　The　results　show　that　under　the　action　of　bidirectional　earthquakes,　the　cracking　and　crushing　of　concrete　in　the　precast　and　assembled　specimens　mainly　concentrate　in　the　joints.　The　skeleton　curve　of　the　precast　and　assembled　specimens　has　no　stable　strength　period,　revealing　twin　kinked　lines.　In　the　direction　of　strong　axis　of　cross-section,　the　energy　dissipation　capacities　of　the　three　specimens　are　approximately　the　same.　The　prestress　basically　increases　in　linear　with　the　increase　of　the　peak　acceleration　before　the　occurrence　of　wire　breakage,　and　the　sudden　increase　of　prestress　will　induce　wire　breakage.　Thus,　it　is　suggested　that　the　stresses　in　the　prestressing　tendons　at　the　locations　of　pier　corners　should　be　taken　as　the　key　points　in　the　anti-seismic　analysis　of　the　precast　and　assembled　PC　box　piers.　©　2019,　Journal　Press,　China　Railway　Bridge　Science　Research　Institute,　Ltd.　All　right　reserved.