The deep structure and its density of South China block and the north margin of the South China Sea is important to understand the regional tectonic evolution and interaction of continent and oceanic plate. The density structures also provide the basic parameters for geoneutrino flux estimation in Jiangmen, China. Based on the gravity data, we inverse the 3D density structure and give the basic geology structures in the study region. The geology structures and the rock physical properties from previous geophysical works are used for constrains in this study. In the final result, we give the density structure from Crust to the upper Lithosphere.