As the surface response of the earths internal dynamics, fault play an important role in the formation and evolution of faulted basins, and they often become the inducing factors of geological disasters such as earthquakes and landslides. Based on the existing multi- channel seismic data, the structural characteristics of the Qiongdongnan fault zone on the southeast side of Hainan Island are comprehensively analyzed in this paper. The results show that the Qiongdongnan fault zone is roughly distributed along the northern boundary of the Qiongdongnan basin on the plane, and is disconnected by a EW- trending fault, dividing it into two sections. It was highly active in the Early Cenozoic and ceased activity in the Late Miocene, and the activity intensity of the western fault was significantly greater than that of the eastern segment of the fault. In addition, the western segment of the fault was accompanied by flower- like structures from the Late Eocene to the Oligocene, which may be related to the rapid sinistral strike- slip activity of the Red Rive fault zone in the west during this period. Combined with the characteristics of free air gravity anomalies in the northern part of the South China Sea, it is inferred that the Qiongdongnan fault zone belongs to the extension of the Binhai fault zone in the northwest part of the South China Sea, and the Qiongzhou Strait fault located in the north of Hainan Island should be the extension of the Lianhuashan fault in the northwest part of the South China Sea. Based on the current research status of Binhai fault zone, it is suggested that the Binhai fault zone offshore outside Yangjiang and Qiongdongnan fault zone can be selected as the drilling target area for future scientific drilling experiment, with cores drilled on both sides of the fault and the fracture zone. The drilling results can provide supports for further determining the extension direction of the Binhai fault zone in the northwest of the South China Sea, and for a more comprehensive seismic risk assessment of the Binhai fault zone in the future.