Abstract: According to the lastest 5 280 kilometers of super 3D seismic data from the Qikou Sag,we found that the faults in the sag could be divided into four levels in the sag and the trend of each fault is slightly different from the others and the north-east fault dominates. In cross profiles, there are four types of faults: the plane ones、shovel-like ones、slope flat ones and complicated slope flat ones. There are three kinds of volcanic rocks in the Neogene deposits in the sag in the forms of volcanic vent、basalt sheet, and basalt laccolith respectively. Buried hill drape anticlines and flower structures have been discovered.