Abstract: Two major types of late Mesozoic continental margin can be distinguished in southern Xizang. One is the Pacific-type （active） continental margin characterized by a typical trench-arc system at the northern side of the Yarlung Zangbo suture,and the other is the Atlantic-type （stable） continental margin characterized by continental shelf-slope-rise at the southern side. Their structural and sedimentary units are differnt, as shown in the following table: This paper further discusses the characteristics of sedimentary, formations,tectonic deformation and evolution history of either enviroment according to the data of stratigraphic, sedimentary facies, paleontology, paleomagnetism and isotope geochronology.