Interlaminar behavior of paulownia wood sandwich can be enhanced by grooves arranged on the surface of the paulownia wood core. Three kinds of silane coupling agents are used by three different ways in order to improve the interface furtherly. All the specimens are manufactured by VARIM process. DCB method is used to measure the interlaminar energy release ratio(ERR) between the face sheet and paulownia wood core. By comparing the ERRs, the way that core surface pretreated by agent-added resins gets the most effective improvement. By analyzing the component of the ERRs, the improvement mostly comes from the interfaces of glass fibers and vinyl resins left in the grooves. The adhesion of the vinyl resin and paulownia wood gets little benefit from the coupling agents.