Abstract: Based on a study of geometric and kinematic characteristics of the extensional structure in the east and west sections of northern Nansha block, the basic models and the dynamics of the Cenozoic extension in South China Sea (SCS) area are discussed in this paper. It is proposed that the evolution of extension includes a pure-shear mod el in late Cretaceous-early Oligocene and a simple-shear model after mid-Oligocene in the east section. The pure-shear extension was initiated by the delamination of the subducted slabs of paleo-Pacific plate. It yielded a number of half-grabens which distributed symmetrically on both sides of the southwest basin (SWB) of SCS. And the upper crust and lithospheric mantle on both sides of SW B had undergone uniform extensional deformation. The simple-shear extension, which was caused by further upwarping and partial melting of the hot asthenospheric mantle and by the collision of Indian plate with Eurasia plate in Tibet Plateau, resulted in asymmetrical extensional deformation Oil both northern and southern margin of central basin of SCS. In the northern margin, there are several different plane assemblage types of half-grabens, including series-type, parallel-type, en echelon-type, face-to-face-type and back-to-back-type. But there is only one kind of plane normal faults in the eastern section. This is different from the western section which separated from the eastern section by the Zhongnan fault. In t northern and southern margin of eastern SCS, the extensional deformations of the crusts were evidently nonuniform with that of the lithospheric mantle under them.