The　reflection　and　transmission　properties　of　acoustic　wave　in　the　trilaminar　plate-like　adhesive　structure　with　a　linear　viscous　adhesive　layer　and　the　upper　and　lower　substrates　were　the　same　kind　of　material　were　studied　when　longitudinal　wave　vertical　incident.　Based　on　the　quasi-static　model　(QSM)　of　the　adhesive　interface　and　the　constitutive　equation　of　the　isotropic　linear　viscous　body,　the　expressions　of　the　longitudinal　wave　reflection　and　transmission　coefficients　with　the　coefficient　of　viscosity　and　bulk　modulus　were　derived.　Firstly,　the　QSM　and　the　exact　solutions　of　the　longitudinal　wave　were　compared　with　each　other　to　explain　the　applicable　conditions　of　the　QSM.　Secondly,　the　effects　of　relative　quality　of　interface　on　acoustic　wave　reflection　and　transmission　coefficients　were　considered,　by　taking　and　not　taking　the　fore-mentioned　factor　into　consideration,　under　the　condition　of　different　interface　contact　forms　(perfect　connection　and　viscous　weak　bonding).　Then,　the　influence　of　parameters　changes　of　viscous　adhesive　layer　on　the　reflection　and　transmission　properties　of　the　longitudinal　wave　was　analyzed.　Finally,　the　method　of　identifying　the　interface　form　in　smaller　frequency-thickness　product　range　which　was　less　than　0.1　MHz-mm　was　briefly　interpreted.　The　results　show　that　the　QSM　is　suitable　for　the　detection　of　smaller　frequency-thickness　product.　Whether　the　relative　mass　of　the　interface　is　considered　has　little　effect　on　the　reflection　and　transmission　characteristics　of　the　longitudinal　wave.　The　interface　forms　could　be　effectively　identified　by　using　the　method　of　reflection　or　transmission　coefficient　of　longitudinal　wave　combined　with　QSM　at　specific　frequency-thickness　product.　The　research　results　could　provide　a　theoretical　reference　for　the　detection　of　the　adhesive　structure　by　longitudinal　wave　vertical　incident.　©　2017,　Chinese　Society　for　Composite　Materials.　All　right　reserved.