Abstract：In the study of the 3-D velocity structure in the mantle of East Asia, West Pacific Ocean and the globe using the high-resolution tomographical techniques of both natural seismic surface and body wave, the authors discovered a giant composite mushroom-shaped low-velocity mantle plume with the depth of over 2000 km, which, combined with the indicators of geology, geochemistry, and geophysics, is named the South China Sea composite mushroom-shaped mantle plume. This paper describes geological, geochemical, and geophysical features of the plume, divides it into such parts as the tail, the main body, the head, the mantle apophysis, and the basalt hot spot, develops a tentative 3-D geometric structural style for the plume, and discusses the dominant role that the plume and its derived mantle dynamics have played in the basin spreading of the South China Sea and the impact of the interaction among the Eurasian, the Philippine, and the Indian-Australian plates on the basin evolution.