Abstract: The northern slope of the Lingshui Sag in the Qiongdongnan Basin develops a series of NWW-SEE trending strike-slip faults. However, previous studies have lacked systematic characterization of these structures, and their role in hydrocarbon accumulation in the middle-shallow layers remains unclear, hindering exploration progress in the shallow sequences. Based on high-resolution 3D seismic data, this study conducts detailed structural interpretation to systematically analyze the geometric and kinematic characteristics of the southern strike-slip fault zone, with a focus on its control mechanism on hydrocarbon accumulation in the middle-shallow layers (Yinggehai Formation-Ledong Formation).The results indicate that the southern strike-slip fault zone exhibits a dextral left-stepping en-echelon distribution, characterized by typical transtensional features and negative flower structures in cross-section. Integrated with regional tectonic evolution analysis, its main active period is determined as the Ledong Formation depositional stage (approximately 1.8 Ma). This study is the first to systematically propose that the strike-slip fault system exerts four key controls on middle-shallow hydrocarbon accumulation: ① It serves as the main vertical migration pathway, connecting deep-source rocks of the Yacheng–Lingshui formations, with geochemical evidence confirming its role as the core channel for upward hydrocarbon migration; ② It controls the development of various trap types, including fault blocks, fault noses, and en-echelon anticlines on the descending side, while promoting the formation of lithologic traps through tilting; ③ Associated structural fractures effectively improve the physical properties of fine-grained reservoirs, forming fractured mudstone gas reservoirs; ④ Quantitative evaluation shows that, although the faults extend to shallow depths, thick regional mudstone caprocks and high normal stress on fault surfaces jointly provide effective sealing, ensuring favorable preservation conditions. In conclusion, the southern strike-slip fault zone is a key geological element controlling hydrocarbon migration and accumulation in the middle-shallow layers of the northern Lingshui Slope. The overlapping segments of the fault zone, integrating efficient migration, reservoir improvement, multiple trap types, and good preservation conditions, represent the most favorable targets for future hydrocarbon exploration. This study enhances the understanding of strike-slip fault control on hydrocarbon accumulation in the Qiongdongnan Basin and provides theoretical guidance for exploration in the middle-shallow layers of the study area.