Abstract: Data from cores,well logs,paleontology and seismic survey have been comprehensively studied in this paper to reveal the evolutionary history of the Oujiang Sag in the Paleogene.Sedimentary facies,such as deltaic,fan deltaic,lacustrine,coastal and shallow marine facies were recognized.The tectonic evolution and filling history of this region in the Paleogene can be divided into three stages.In the early Paleocene,the prototype of the sag was formed by faulting and filled with deltaic-lacustrine-fan deltaic depositional systems.During the stage from the middle to late Paleocene,with the gradually weakening of the faulting activity,deltaic-coastal-shallow marine-fan deltaic depositional systems were developed.By the end of the late Paleocene,deltaic deposition prevailed due to the expansion of the Fujian uplift.In the Eocene,deltaic-coastal-shallow marine depositional systems were well developed owing to the depression of the sag.