Tunnel　portal　sections　often　suffer　serious　damage　in　strong　earthquake　events.　Earthquake　waves　may　propagate　in　different　directions,　producing　various　dynamic　responses　in　the　tunnel　portal.　Based　on　the　Galongla　tunnel,　which　is　located　in　a　seismic　region　of　China,　three-dimensional　seismic　analysis　is　conducted　to　investigate　the　dynamic　response　of　a　tunnel　portal　subjected　to　earthquake　waves　with　different　vibration　directions.　In　order　to　simulate　the　mechanic　behavior　of　slope　rock　effectively,　an　elastoplastic　damage　model　is　adopted　and　applied　to　ABAQUS　software　by　a　self-compiled　user　material　(UMAT)　subroutine.　Moreover,　the　seismic　wave　input　method　for　tunnel　portal　is　established　to　realize　the　seismic　input　under　vertically　incident　earthquake　waves　with　different　vibration　directions,　e.g.,　S　waves　with　a　vibration　direction　perpendicular　or　parallel　to　the　tunnel　axis　and　P　waves　with　a　vibration　direction　perpendicular　to　the　tunnel　axis.　The　numerical　results　indicate　that　the　seismic　response　and　damage　mechanisms　of　the　tunnel　portal　section　are　related　to　the　vibration　direction　of　the　earthquake　waves.　For　vertically　incident　S　waves　running　perpendicular　to　the　tunnel　axis,　the　hoop　tensile　strain　at　the　spandrel　and　arch　foot　and　the　hoop　shear　strain　at　the　vault　and　arch　bottom　are　the　main　contributors　to　the　plastic　damage　of　the　tunnel.　The　strain　is　initially　concentrated　around　the　tunnel　foot　and　spandrel,　before　shifting　to　the　tunnel　vault　and　bottom　farther　away　from　the　tunnel　entrance.　For　vertically　incident　S　waves　running　parallel　to　the　tunnel　axis,　very　large　hoop　shear　strain　and　plastic　damage　appear　at　the　tunnel　haunches.　This　strain　first　increases　and　then　decreases　with　distance　from　the　tunnel　entrance.　For　vertically　incident　P　waves　running　perpendicular　to　the　tunnel　axis,　the　maximum　damage　factor　of　the　slope　rock　and　the　maximum　plastic　strain　of　the　tunnel　are　significantly　lower　than　for　S　waves.　Moreover,　with　increasing　distance　from　the　tunnel　entrance,　the　plastic　damage　to　the　tunnel　lining　rapidly　decreases.