Abstract: Using the high-resolution 2D seismic data currently acquired and upon the basis of the regional tectonic background, the comprehensive seismic data interpretation for the Beikang Basin is carried out. Main unconformity interfaces are identified, stratigraphic age redetermined, and their geological significance to oil and gas geology discussed. The results suggest that there are six unconformities in the region respectively corresponding to the Liyue movement, Xiwei movement, South China Sea movement, Nansha movement, Wan'an movement and Guangya movement. Among them, the T₃ unconformity is the boundary of the post-spreading period of the South China Sea caused by the Nansha movement, marking the cessation of the South China Sea spreading. Well-seismic correlation of Well Mulu-1 shows that the unconformity surface (T₃) corresponds to the Middle Miocene unconformity surface (MMU) of 16 Ma characterized by high amplitude, strong erosion and large undulation. Abrupt changes in stratigraphic structure, occurrence, and seismic reflection characteristics occur above and below the interface. It is the boundary face between the deformed and undeformed strata, and bears great significance to local structures and hydrocarbon accumulation.