abstract:Recent researchers revealing, there are many complex structures in the South China Sea (SCS). There are folds, trenches, mud appearances, mud volcanoes, gas hydrates and faults. Why is this region so complicated? As we know, this area is affected by the dynamic plates. The most important reason is due to subduction between the Eurasia Plate and Philippine Sea Plate. It creates many big structures in the South China Sea, including the Manila Trench, fossil South China Sea ridge and Luzon volcano Arc, etc. In this study, we analyze the seismic data to understand the tectonics in the SCS. Through the Continental Shelf Survey Program, we deployed 68 Ocean Bottom Seismometers (OBS) on the seabed in the SCS in 2007 and 2008. From northwest to southeast, the profiles are distributed in the depth of 1500m to 4200m. We assembled the Multi-Channel Seismic (MCS) data and Ocean Bottom Seismometer (OBS) data. The MCS data displays the shallow stratum. The OBS data is about the P-wave and S-wave reflection and refraction used to estimate the structure in the crust and upper mantle. In the data, we obtain that there are some old igneous rock besides the horizontal sedimentary beds. However, the South China Sea is a Miocene-Eocene back-arc basin and belongs to an asymmetric rift of the continental margin. It started to spread in about 32 Ma and ended in about 15 Ma. A thin sedimentary rock lay over the seabed. We used the MCS data to establish the initial model and extend to the deep, in an aim to better understand the evolution of the SCS.