Abstract: On the basis of the latest multi-channel seismic profiles and geophysical data such as gravity, magnetism and topography, the spatial distribution characteristics of faults, the development period of faults, the internal structural deformation feature of faults and deep crustal structure in the southern Zhongsha Bank (ZB) were revealed, and the formation mechanism of the faults was also discussed. The results show that the tectonic property of the southern continental margin of ZB is non-volcanic passive continental margin. From northwest to southeast, the crustal properties change from thinned continental crust to oceanic-continental transitional crust and then to normal oceanic crust. The depth of Moho discontinuity rises rapidly from 26 km beneath the ZB to 10-12 km beneath the ocean basin. The obvious negative gravity anomaly area from the steep slope of the ZB to the coast front is the oceaniccontinental transitional zone, and the boundary of gravity anomaly change from high value negative anomaly to low value positive and negative anomaly in the ocean basin is the oceanic-continental boundary. There are four sets of deep and large normal faults with stepped sea-dipping in the southern part of the ZB, which were mainly developed in the Late Oligocene to the Middle Miocene. The early extension of the fault development mechanism was related to the NS-trending extension of the sub-basin in the eastern South China Sea (SCS), and the later compressive stress was related to the NW-trending subduction of the Philippine plate towards the SCS. This study is helpful to the better understanding of the expansion history of the South China Sea basin and the types of passive continental margins in the SCS.