Abstract: The Kyushu-Palau Ridge (KPR) is an excellent place to study the initiation of plate subduction, and thus a unique natural laboratory for developing the plate tectonic theory. Based on a thorough review of literatures, we tried in this paper to reveal the solid vs. liquid structure of the lithosphere using the geophysical data by OBS and OBEM along a regional transection passing through the West Philippine Basin, the KPR, and the Perce-Vela basin. Combined with geochemical studies and computational geodynamic simulations, the characteristics of the deep subducted slabs, the different oceanic lithosphere, the corresponding magmatic activities and mechanism as well as the flux and cycling of the subducted materials are investigated. Upon the basis, a complete evolution model including subduction initiation, island arc splitting, and the back-arc seafloor spreading is proposed in this paper for the tectonic evolution of a subduction zone.