Through comprehensive study on the seismic data，well logging data，sedimentary facies，paleogeomorphology analysis，the paleo ravine and slope-break zones of the mid-Miocene in Qiongdongnan basin were identified，and the developmental feature，distribution rule and control over sedimentary of the paleo ravine-slope break zones were emphatically analyzed. The hydrocarbon reservoir forming conditions and distribution regularity of the lithologic reservoirs developed under the environments were discussed. The results show that there are three types of paleo ravine，including“V”shape，“U”shape and dish-like shape，and“V”or“U”ravine generally developed in Ledong sag and Lingshui sag，while the dish-like ravine developed in Baodao sag. Three types of slope-break zones developed，such as depositional slope-break zone，fault slope-break zone and flexure slope-break zone with certain distribution regularity. The depositional slopebreak zone mainly developed in Ledong sag and Lingshui sag；the fault slope-break zone developed in Lingshui sag and Songnan sag；and the flexure slope-break zone developed in Baodao sag. Different slope-break zone has different influence on sedimentary.Submarine fans with rich sand developed in Ledong sag and Lingshui sag and are the main reservoir in the study area，which were controlled by depositional slope-break zone with strong hydrodynamic environment. They developed widely with characteristics of coarse grain and good physical property. Submarine fans in Lingshui sag were controlled by fault slope-break zone to some extent，which developed at the downthrown of fault named lobate complex fanbodies. Submarine fans in Baodao sag with bad physical property were controlled by flexure slope-break zone where the hydrodynamic power was weak，and thus have fine grains. Comprehensive analysis shows that some zones in Ledong sag and Lingshui sag near the slope-break zones are favorable to form lithologic reservoirs，and should be the future exploration targets in deep waterarea.