To clarify the population size and regional distribution of finless porpoise (Neophocaena asiaeorientalis) in the estuary of Yangtze River, two surveys were performed in the water surface of 23884km2 in size from June 8th to 11th and September 12th to 19th in 2012 respectively. Eight porpoises in five groups were witnessed in June while no animal was found in September. According to the estimation based on transect of 805km in length, 61 individuals were estimated in June. In addition seven remains and five dead records of the porpoises were collected From the riverside of the Yangtze River in the entire year 2012. Two Yangtze finless porpoises(N. asiaeorientalis asiaeorientalis) and three East Asian finless porpoises (N. asiaeorientalis sunameri) were identified based on the external characteristics of remains which were relatively intact. The results suggest that the water areas west to Chongming Island and northwest to Changxing Island might be the core distribution regions of Yangtze finless porpoise in the estuary area.