Abstract: In the southeastern margin of shallow water area in the Qiongdongnan Basin, a small lacustrine fault-controlled Eocene Lingtou Formation called Baodao 15 Sag which revealed that the rich petroleum in the Paleogene,due to the marginal sag prone to strong erosion, uneven uplift and late transformation, the geological structure became more complex. During the fracture and depression period, the Lingtou Formation strata underwent intense tectonic deformation under the combined action of "strike-slip and extension", and seriously restricted the evaluation and exploration process of source rocks.Based on the analysis of the structure, fault characteristics, prototype basin of the Lingtou Formation and the process of tectonic deformation, the potential for petroleum exploration and the favorable exploration directions were analyzed.Research shows that ① Baodao 15 Sag is transitioning from a double-faulted graben during the rifting period to a southern faulted and northern super-semi-faulted graben during the fault-controlled transition period which divided into eastern and the western tectonic zones by the central strike-slip fault. The uncoordinated tensile deformation of the eastern tectonic zone mainly occurred in the Eocene to Early Oligocene, formed a shingled slip sag system. The tensile deformation of the western tectonic zone mainly occurred in the Eocene, formed a domino-like small forward fault depression system; ② By using the trend extrapolation method to restore the erosion boundary and erosion volume, the semi-deep laculacine source rocks in the Eocene prototype basin were widely distributed in the concave area, with an average TOC of 0.2% to 14.2% and R_o of 0.6 to 1.8%, the area of mature source rocks was nearly 92 square kilometers, and the potential of crude oil resources was approximately 56 million tons; ③ The reservoir and cap assemblage of the Lingshui-Yacheng Formation is well developed which resource volume of the hydrocarbon supply unit is abundant, the Lingtou Formation in the southern sag zone has the characteristic of "self-generation and self-storage" within the source, the two favorable zones are the next step of petroleum exploration in this area.