Abstract: The strata of Oujiang Sag are divided into three sequences by identifying the sequence surfaces and the most flooding faces based on drilling data, logging data and seismic data. The sequence faces are recognized in the seismic section, they are T₂⁰, T₄⁰, T₄², T₅⁰. Each sequence is divided into three tracts based on the changes of lithology facies, overlying model and so on. Due to the research on the drilling cores, the logging data and paleontologic evidence, we define some depositional systems such as delta, lacustrine and marine in the Paleogene System of Oujiang Sag. Yueguifeng group consistss of delta facies and lacustrine facies sediments, Lingfeng group and Mingyuefeng group consists of delta facies and littoral facies sediments, Oujiang group and Wenzhou group consists of delta facies and littoral facies sediments, and neritic facies deposited in the east sag. Sediments sourced from west and northwest. In the Paleogene System, two large marine transgressions happed in middle Paleocene and middle Eocene.