Migratory waterbirds protection is essential for biodiversity protection. It is particularly important to clarify the population dynamics based on the monitoring of population size and age ratio, so as to scientifically evaluate its population trend and formulate long-term protection strategies. Wetlands in the Yangtze River floodplain are one of important winterings for waterbird species on the East Asian-Australasian flyway. In this study, the overwintering waterbird species in 87 wetlands were monitored for a long time (in each winter from 2003 to 2019) by the field investigation and literature review, and the age ratio and the mortality of 10 large-bodied waterbirds (6 geese and swans species, Swan Goose Anser cygnoides, Bean Goose A. fabalis, Greylag Goose A. grus, Greater White-fronted Goose A. albifrons, Lesser White-fronted Goose A. erythropus, and Bewick's Swan Cygnus columbianus; 4 cranes species, Siberian Crane Leucogeranus leucogeranus, White-naped Crane Antigone vipio, Common Crane Grus grus, and Hooded Crane G. monacha) were evaluated. The results are as follows:(1) the population size of 7 species of waterbirds (Swan Goose, Greater White-fronted Goose, Lesser White-fronted Goose, Bewick's Swan, Siberian Crane, White-naped Crane, and Hooded Crane) decreased, 3 species of waterbirds (Bean Goose, Greylag Goose, and Common Crane) increased; (2) In 2016-2019, the average age ratio of the declining (N=7) and rising (N=3) groups were 0.168 and 0.173, with no significant difference between the two groups (P=0.601); (3) In 2016-2019, the average mortality of the declining and rising group were 0.245 and 0.125, with significant difference between the two groups (P=0.006). This study showed that the main factor leading to the decline of overwintering waterbird species population in the Yangtze River is high mortality, not low reproductive success rate. It is suggested to strengthen the protection of the 7 declined waterbirds in the future, collect the time, place and the cause of death, and further study the factors caused high mortality.