By　in-situ　investigation,　it　is　found　that　portal　sections　of　mountain　tunnels　are　the　weaker　parts　of　mountain　tunnel,　during　earthquakes,　which　leads　to　slope　unstability　and　lining　damages.　Large　scale　shaking　table　model　tests　were　performed　on　tunnel　portal　parts.　Results　show　that　an　amplification　effect　of　acceleration　exists　at　the　area　with　some　distance　from　the　entrance　of　the　tunnel.　This　effect　may　produce　non-uniform　vibration　along　the　lining.　The　analysis　of　the　strain　show　that　the　tunnel　lining　structure　is　mainly　subjected　to　transverse　stress.　And　seismic　additional　stress　mainly　concentrated　at　arch　waist　and　arch　feet,　which　could　be　seen　as　weak　parts　in　seismic　design　of　lining　structure.　During　the　test,　lining　at　the　area　with　some　distance　from　the　entrance　of　the　tunnel　damaged　first.　And　so　such　amplification　effect　did　not　result　in　greater　inner　force　in　tunnel　structure.　Thus　the　effects　of　inertial　force　on　structure　inner　force　is　rather　small　for　tunnel　portal　parts.　Displacement　of　slope　surface　at　tunnel　portal　section　increases　according　to　parabolic　law　with　the　slope　height.　Lining　structure　is　deformed　into　oval,　of　which　the　biggest　deformation　happens　at　the　arch　waist　and　arch　feet.　With　stepwise　loading　of　seismic　wave,　a　pushed　type　sliding　happens　at　the　tunnel　portal　section,　which　results　in　tunnel　structure　damages.　Existence　of　construction　joints　consumes　part　of　additional　internal　force　arising　from　deformation　of　surrounding　rock,　which　is　of　advantage　for　anti-seismic　performance　of　lining　structure.　Test　results　may　give　a　reference　to　seismic　design　of　tunnel　portal　section　in　mountain　tunnels　in　weak　surrounding　rock.　©　2016,　Science　Press.　All　right　reserved.