Abstract: The Chinese merganser (Mergus squamatus) is a rare species,it has a limited distribution area and in the International Red Data Book as a threatened species.The number of which shows a tendency to reduction.From 1962 to 1991,the population,distribution was studied in the Changbai Mountain.They inhabit mostly in the Tou Dao Bai river,San Dao Bai river,Gu Tong river and Mangjiang river in the mixed forests of conifers and broad-leaved species in Changbai Mountains.According to the 1977-1979 survey in Changbai Mountains region,the population density of the Chinese merganser on the Tou Dao Bai river was 0.72 ind/per km,1989 was 0.66 ind/per km,1990 was 0.63 ind/per km,1991 was 0.50 ind/per km,is falling gradually.The reason population density is falling was due to deforest,the breeding habitats of this species are being destroyed and popular disturbance.