Abstract: The Xihu depression lies as a major petroleum depossion in the northwestern part of the East China Sea shelf basin. According to electrical properties, palaeontological fossils, seismic facies, global seal-level changes and palaeoclimatic responses, the Palaeogene Huagang Formation in the Xihu depression, East China Sea may be redivided into two second-order sequence boundaries including SSB4 and SSB5, and two third-order sequence boundaries including SB6 and SB5. Correspondingly, three third-order sequences have been distinguished in the Formation, including SQ4, SQ5 and SQ6. This study helps improve our knowledge of the sequence stratigraphic division and the redelineation of favourable hydrocarbon reservoirs within the sequence stratigraphic framework in the study area.