The origin of the South China Sea has long been a hot subject of research, as it is related to the interaction of two large convergent zones, the Tethys and the Circum-Pacific, as well as to the geodynamics of the marginal seas of the West Pacific. The Sea of Japan and the South China Sea, as part of the inner zone of the West Pacific marginal seas, have many common features such as the age, shape and topography of the sea bas-in , the multi-axial and multi-stage seafloor spreading, westward propagating crustal extension, and the mantle geochemistry. These may imply their common origin. The South China Sea basin has a cuneiform shape. The seafloor spreading in the South China Sea and the rifting of its continental shelf were characterized by south-ward jumping and westward propagating development. The crustal extension decreased westward. These may be portrayed as a westward tipping scissors, whose opening was caused by the splitting of the East Asia conti-nental margin under approximately N-S oriented dextral shearing. Numerous N-S running dextral faults devel-oped in the Indochina Peninsula and within the South China Sea basin when it was opening, indicative of the existence of dextral stress at the time. The present eastern border of the South China Sea is occupied by a N-S running subduction zone, not a large dextral fault; this may be ascribed to the destruction of previous structure by the docking and obduction of the Philippine Archipelago along the present Manila trench. Since the Late Mesozoic, convergence toward Eurasia with various direction and speed occurred in the West Pacific domain, the Indian segment of the Tethys domain, and the Australian segment of the Tethys domain. These convergent forces competed and compounded each other, forming the geodynamic background for the development of " large shearing" in the margin of East Asia. This shearing was characterized by the alternative sinistral transcompression and dextral transtension, and might be driven by convergence-induced mantle flow. In the period when the influence of the India-Tibet convergence predominant, the East Asian margin was split under the stress field of dextral transtension, and then opened the South China Sea and other seas of the inner zone of the West Pacific margin