Abstract: Base on the data of seismic profile, the paper analyses the characteristics of the structures and activities of active faults of Liyuetan and its adjacent area, the Southern South China Sea. Two groups of active faults in NE and NW directions exist in the area. The NE active faults, formed during the extension of the epicontinent of southeastern China in the late Cretaceous and early Paleocene, are mainly exists in coral reef areas of Liyuetan and its adjacnet area. It had intensive activity in late Cretaceous and early Paleocene, and kept active in late Tertiary. It is mainly an expanding-shearing fault and now has medium and weak activity. The NW faults mainly exists in the area near Palawan. It is an extending-shearing and left-slip fault which cuts the basement. It had intensive activity from early Miocene and Pliocene. It is still active in Quaternary but only a fault with weak activity. There are only a few SN faults in this area. The area has records of volcano and few earthquake activities in the history.