In order to better analysis the information of the underground source reflected by gravity abnormity and the structure of the north marginal basins in South China Sea, this paper adopted the method of the two-dimensional wavelet decomposition technique. Through resolving the gravity abnormity in the north marginal basins in South China Sea, and combining the topography and geomorphology of the study area, this paper discussed the basin structure and the geological characteristics of rock mass distribution. The results show that the fourth order transform approximation is mainly composed of the information of Moho undulations, and the wavelet transform details is mainly composed of the information of sedimentary-base undulations.oft-com:office:office" />