Abstract: Poyang Lake is the main overwintering area of migratory birds in East Asia. There are about 350000 migratory birds belonging to 105 species in every winter. The unique hydrological processes and a lot of the shallow lakes in the delta of the river mouth where Ganjiang River flows into Poyang Lake are the important conditions for the formation of wetland ecosystem characteristics and the winter migratory birds habitat in Poyang Lake. In this paper, the mechanisms for the hydrological processes effect on wintering migratory birds have been studied and the feeding object and overnight roost for all kinds of migratory birds have been analyzed, combined with monitoring data of migratory birds and the hydrologic data each year in Poyang Lake, using the quantitative and qualitative methods. The results show: 1) It is most favorable for the overwintering migratory birds and the number of wintering birds is the largest, when the Poyang Lake is at a normal water level year. 2) It is unfavorable for the overwintering migratory birds due to lack of foods and the wild gooses, wild ducks and swans are affected maximally, so the number of wintering birds is small, when the lake is at high water level in wet season. 3) The number of overwintering migratory birds may be reduced by feeding difficulties for storks, swans, snipe and so on, when the lake is at high water level in dry season. 4) If water level in the shallow lakes can be managed scientifically, wintering migratory birds will not have significant adverse impact, when dry season water level of Poyang Lake is low, but does not favor the migratory birds, if the water level is too low in Poyang Lake.