Abstract: Inspired by the exploration of the outer slope zone in Xihu Sag, 3D seismic acquisition has been deployed in the outer slope zone in order to obtain more exploration discoveries. Based on the analysis of stratigraphic development characteristics, sedimentary facies analysis was carried out by combing logging data and core data. Subtle traps identification was carried out by using wave impedance inversion and seismic forward modeling results, and a comprehensive evaluation of stratigraphic overlap traps was carried out by analyzing accumulation conditions such as oil source diversion and physical properties. The results indicate that Pinghu Formation in the study area has developed deltaic sedimentation, while Huagang Formation has developed braided river sedimentation. Four different stratigraphic overlap type subtle traps were identified in Pinghu Formation and Huagang Formation. The comprehensive evaluation suggests that the subtle traps (stratigraphic overlap traps) which are identified in the outer slope zone have a resource scale of nearly 30 billion cubic meters, these resources expand the exploration potential of Xihu Sag and lay a foundation for future exploration discoveries.