Abstract: Granitoids are the main component of the continental crust, and the key problem for understanding the structure，composition and evolution of the continental lithosphere．Late Mesozoic calc-alkaline magmatism is wel1 developed in the coastal area of southeastern China, and is similar to the magmatism developed in the Basin and Range of North American． During the previous studies on the granites in the coastal area of southeastern China，however, 1ittle attention has been paid to the temporally and spa1ial1y coexisted A—type granite，gabbroic stocks or dikes, as well as the bimodal volcanic rocks (basalt-rhyolite composite lavas). The authors have been studying the granites in the coastal area for many years and noticed recently that this region experienced extensive crust-mantle interaction at the crust-mantle boundary, and underplating was the important process which involved in the chemical and thermal contributions from the mantle to the crust. The petrography, geochemistry and isotope studies for the gabbroic granulite from Qilin basaltic pipe in the same region，and integration with the regional geophysical, lava indicate that gabbroic granulites were formed by underplating of basaltic magmas at the bottom of the crust at ca 112 Ma．This is consistent with the extensive granitic magmatism in the Late Mesozoic time along the coasta1 area of southeastern China. Therefore，underplating plays important part in the evolution of the continental crust of southeastern China． Most of the granit formed in the earlier stage of Late Mesozoic time in southeastern China are S-type granites. They might be generated from the partial melting of the deeper crust material under the compressive tectonic setting. While the extensive I-type and A-type granitic magmatism in the coastal area of southeast China is closely related with back—arc extension，lithosphere thinning and asthenosphere upwelling，which may have been induced by the earlier stage subduction of the Pacific plate towords the Eurasian continent. In fact，the late Mesozoic magmatisms along the coastal area have an essentially extension related bimodal character，and apparently，the genesis of granities in the crustal area of southeastern China is directly related with the basaltic magma underphlating. The source age of 1O0～110 Ma of southeast China may represent the transition age of tectono-magmatism rom” compression-crust thicking-continental crust re-melting” to “extension-lithosphere thinning-bimodal magmatism”.