Abstract: The Changsha reach, situated at the downstream of the Xiangjiang River， is influenced by the combinational hydrologic characteristics of the Xiangjiang River and the Yangtse River as well as the Dongting Lake. Since the impoundment of the Three Gorges reservoir， the Changsha reach has suffered so severe drought, which has resulted in the water level decline, which has broken the historical lowest records. According to the variation of the relationship between water level and discharge, the monthly average water level and the lowest water level， the variation law of the low water level in the Changsha reach and the impacts given by the impoundment of the Three Gorges reservoir on the low water level are studied in this paper. The results indicate that the water level under the same discharge, the monthly average water level and the lowest water level all decreased year by year. The lowest water level along the Changsha reach has no direct relationship with the variation in the water level after the impoundment of the Three Gorges reservoir， but with the riverbed entrenchment caused by the running of the hydroprojects located on the Xiangjiang River and the disordered sand mining in the river.