Abstract: On June 1-15 and October 20-21,2003,the Three Chrge reserwir was filled with water.In June,the discharge at Datong hydrological station reduced by 37 percent,and the lasting time of freshwater at the observation station decreased by 40 percent.The maximum salinity and average salinity increased 3 times and 6 times,respectively.In October,the discharge at Datong station decreased by half,and the freshwater reurce reduced,too.The maximum salinity increased 3 times compared with the averaged one.This paper discusses the aspects of the discharges along the Yangtze River,the acute change of the discharge,the time affecting the estuary and the affection factors.At last,the conclusion is drawn that the Three Chrge resemvir filled with water reduces the fresh water resource in the Yangtae River estuary.