Abstract: The analyses of paleostructure, paleogeographic and sea level changes in the deepwater area of the Qiongdongnan Basin show that Miocene is favorable for bioherm development. The characteristics of sequence stratigraphic structure indicate that both slope platform margin and fault-controlled platform margin generate in the south of the deepwater area, giving birth to bioherm with obviously different evolution features. As to the fault-controlled platform margin, the Mei2 period is the main beach-forming period, and the Mei1 period is the main bioherm-forming period. As to the slope platform margin, both beach and bioherm develop during the Mei2 period, and the bioherm development scale is smaller; while in the Mei1 period, only beach develops.