Abstract: The wide angle seismic profile OBS2006-3 crossing the Dongsha Rise and the Chaoshan and Chaonan Depressions of South China Sea was completed by the Second Institute of Oceanography, SOA in the autumn of 2006. Based on the inversed velocity model of the whole profile, a more accurate 2D tomography imaging was carried out in this paper for a smaller model and only refracted waves recorded by seven OBS stations in the Chaoshan and Chaonan Depressions were used. The imaging results show that there are three sediment layers in the depression area. The thicknesses of the first two layers of the Cenozoic sediments are very thin, less than 2 km with velocities of 2.2 km/s and 3.6 km/s, respectively. In the Mesozoic sediment layer the velocity increases gradually from 4.4 km/s at the top to 5.4 km/s at the bottom with a maximum thickness of 8 km and can be considered as a horizontal sub-layer. Based on the gravity simulation of OBS2006-3, the average density of the Mesozoic layer in the Chaoshan and Chaonan Depressions is 2.45 g/cm3. The average densities of the profile OBS2006-3 in the crust, the high velocity layer and the upper mantle beneath Moho are 2.86 g/cm3, 3.05 g/cm3 and 3.32 g/cm3, respectively.