Abstract: Structure Y is the largest anticline structure in the central anticlinal belt of Xihu Sag, East China Sea, and also exhibits the most complex structural deformation generated by compressional twisting during Longjing Movement. Previous drilling has revealed complex hydrocarbon-bearing properties in Structure Y with poor understanding of hydrocarbon accumulation patterns, and the migration pathways are still debated. Based on stress field analysis of flexural folds derived from well-penetrated seismic profiles combined with the neutral surface theory, this paper analyzes the characteristics of structural stress. It concludes that early faults developed in Pinghu Formation on both flanks of Structure Y became tensile after Longjing Movement, thus possessing vertical hydrocarbon migration capacity. In zones with high net-to-gross ratios and thick sandbody development, flexural slip prevails during folding and allowing potential lateral hydrocarbon migration. In contrast, in zones with low net-to-gross ratios and thin sandstone development, flexural flow dominates during folding; thin sandbodies are prone to fragmentation into lenticles via shearing, which severely hinders lateral hydrocarbon migration. This study clarifies the hydrocarbon migration patterns of Structure Y and provide valuable guidance for further research on hydrocarbon accumulation in this area.