Abstract: Based on compilation of magmatic lithogeochemical data and the discrimination diagrams for Geo-chemic-tectonic settings, this paper introduces the chemical characteristics,the original types, the tectonic settings for Cenozoic adakitic rocks around South- Easten margin of Sundan Oldland (including Java Island, central part of Kalimantan Island,Sulawesi Island, Lampung Province of Southern Sumatra among Indonesian Archipelago)and north-western part of Vietnam. And the magmatic origin and provenances of these rocks are discussed here. The Cenozoic adakitic rocks within this area consist of C-type (continental) and O-type ( island arc), and the ratios of La/Yb (=2.49 ~ 80.14)vary widely compared to the typical adakitic rocks in Allusion Archipelago. The adakitic rocks in Java Island, central part of Kalimantan Island and Lam-pung Province of Southern Sumatra were formed at island arc and volcanic arc in active continental margin, whereas the adakitic rocks in Sulawesi Island spatially have more varying distribution of tectonic settings:including oceanic island arc, island arc and volcanic arc of continental margin, and rafting valley of back-arc). The origin type of the Cenozoic adakitic rocks within north-western part of Vietnam only have C-type, which belongs to volcanic arc of active continental margin. The arm of this paper is to discuss the margma-tism and its provenances in these areas and suggest that the origin of the adakitic rocks in Java Island, cen-tral part of Kalimantan Island, Sulawesi Island, Lampung Province of Southern Sumatra may be derived from the partly melting of subducted oceanic slab, through partly melting and assimilation of mantle wedge(or adakitic Lower Crust)by melting-assimilation-storage-homogenization process (MASH) in addition to assimi-lation-fractional-crystallization process (AFC), whereas C-type of High-K adakitic rocks in north-western part of Vietnam mainly indicates the stronger crystallization fraction within upper crust.