The Dongting Lake has a high efficiency in regulating runoff of the Jingjiang Reaches of the Yangtze River.Based on the analysis of long-term hydrological data, after the regulation of runoff, the annual average runoff amount, runoff amount of flood season and ratio of runoff amount of flood season to dry season decreased by 26.3%, 32.9% and 32.4%, respectively.Annual average runoff amount and runoff amount of flood season decreased along the liver-All these are quite unique in the main stream of the Yangtze River-The maximum discharge amplitude Q_k is 0.892 in the lower Reaches of the Jingjiang River which is the smallest among the main stream of the Yangtze River.