We analyzed the trend in population change of the Eurasian Spoonbill (Platalea leucorodia) wintering in the Poyang Lake National Nature Reserve between 1985 and 2011, and examined the correlation between its population size and climate variables at that reserve. The climate variables included monthly average air temperature, monthly average maximum air temperature, monthly average minimum air temperature, and monthly precipitation. The results showed that the population size of the Eurasian Spoonbill in the Poyang Lake National Nature Reserve was 4632±470, with a significant linear increase over the period studied and drastic annual fluctuations. There were no significant correlations between population size and climate conditions in the same year. However, we found that climate in wintering areas had a carry-over effect on subsequent population number changes of the Eurasian Spoonbill. The climate in the wintering period was significantly positively correlated with the population size after 1-9 years, precipitation in October was significantly negatively correlated with population size after 2 years, and the average maximum air temperature in December was significantly negatively correlated with population size after 8 years. The results of stepwise linear regression showed that the average minimum air temperature in October 2 years earlier, the average minimum air temperature in November 4 years earlier, the precipitation in November 11 years earlier and the average air temperature in December 4 years earlier were significant predictor factors for population size fluctuations of the Eurasian Spoonbill and accounted for 78.9% of the population size change. The first three variables accounted for 72.1% of the population size fluctuation of the Eurasian Spoonbill. These 2 months represent the primary wintering period when the Eurasian Spoonbill had just arrived at their wintering area. This may be the key period for the Eurasian Spoonbill in which it replenishes its energy. Bad weather in this period may lead to the Eurasian Spoonbill being unable to obtain sufficient energy, which could lead to adverse impacts on population size.