This　paper　investigated　the　seismic　response　of　a　precast　horseshoe　segmental　tunnel　(PHST)　by　using　1-g　shaking　table　tests,　with　a　specific　focus　on　the　transversal　deformation　of　the　PHST　model　(tube).　The　structural　responses　of　the　tube,　including　the　absolute　and　relative　displacements　in　both　the　horizontal　and　vertical　directions　as　well　as　the　flexure　at　the　segmental　connections,　were　investigated　in　this　study.　The　measured　horizontal　responses　of　the　tube　and　the　nearby　soil　were　in　phase.　The　dynamic　response　of　the　tube　in　the　horizontal　direction　was　strongly　affected　by　the　predominant　frequency　of　the　site　and　the　frequency　content　of　the　earthquake　motions.　On　the　other　hand,　the　vertical　responses　at　the　crown　and　the　invert　differed　in　terms　of　peak　values　and　displacement　direction,　indicating　that　the　tube　vibration　in　the　vertical　direction　was　not　governed　by　the　soil.　Furthermore,　the　tube　experienced　horizontal　racking　deformation　as　well　as　compressive-expansive　deformation　in　both　the　horizontal　and　vertical　directions,　which　slightly　increased　flexural　bending　at　the　connections.　However,　the　peak　of　the　most　unfavorable　deformation　corresponded　to　the　peak　of　the　horizontal　racking　deformation.　Therefore,　the　ratio　of　the　horizontal　racking　deformation　to　the　tunnel　cross-section　height　is　recommended　as　an　important　indicator　of　seismic　performance.