The morphology,  sedimentary filling and petroleum geology of the central submarine canyon in the Qiongdongnan Basin were studied using cores, logging, seismic, assaying data and paleontology data. The results show that the canyon, which is located at the central depression of Qiongdongnan Basin, starts from the continental slope of Yinggehai Basin and terminates at secondary basin in northwestern South Sea. The northeast-trending canyon with S shape in plane and V or U shape in cross-section is ca 580 km long, 1~3 km wide at bottom, 6~15 km wide at top, and 400~600 m deep.