Abstract: 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.