The　installation　of　the　buffer　layers　is　of　advantages　to　the　seismic　resistance　of　the　tunnel.　A　set　of　flexible　airbag　loading　system　suitable　for　dynamic　model　test　on　shaking　tables　was　developed　to　simulate　the　gravity　stress　of　tunnel　overburden.　Dynamic　response　mechanism　of　loosen　zone　and　buffer　layers　were　analysed　and　compared　based　on　tests　data　of　acceleration,　additional　strain,　additional　bending　moment　and　structure　failure.　It　could　be　concluded　that:　(1)　Both　the　loosen　zone　and　buffer　layers　did　not　change　the　dynamic　response　rule　and　the　damage　mode　of　tunnel　structures;(2)　Due　to　the　existence　of　loosen　zone,　the　restraint　effect　of　the　surrounding　rock　on　the　tunnel　structure　is　weakened,　resulting　in　the　increase　of　the　deformation　in　tunnel　structure.　The　additional　bending　moment　of　the　structure　increases,　indicating　that　it　is　more　vulnerable　to　damage　in　earthquakes　considering　loosen　zones;(3)　The　installation　of　the　buffer　layers　can　effectively　reduce　the　structure　additional　strain　caused　by　seismic　load,　which　improved　the　mechanical　performance　of　the　structure.　This　layer　coordinated　the　overall　deformation　of　the　tunnel　and　improved　the　seismic　performance　of　the　structure;(4)　In　such　problems,　that　tunnel　structure　surrounded　by　a　softer　medium　layer,　stiffness　is　the　key　factors　which　could　be　concluded　in　material　thickness　and　strength.　©　2018,　Science　Press.　All　right　reserved.