Abstract: Based on the water level and flow data of Jianli, Chenglingji and Luoshan stations from 1990 to 2017, this article analyzed the hydrological conditions and the mutual supporting effects of the intersection area between The Dongting Lake and the Yangtze River under the operation of the Three Gorges Reservoir by using the methods of difference, flow anomaly and correlation coefficient analysis. Compared with the pre-operation of the Three Gorges Reservoir we have the following results: (1) The water level and flow of Jianli, Chenglingji and Luoshan stations in the river-lake junction area have changed after the operation of the reservoir under different flow and water level. The water level decreases more than 0.50 m under different flow rates, more than 2 000 m3/s in the different water levels during the pre-discharge period, more than 1 000 m3/s in the different water levels in the recharge period. The rising range of water level is between 0.50-1.00 m; (2)After the operation of the Three Gorges Reservoir, the correlation coefficients between river level and flow at all the three stations are between 0.50-0.96; and the correlation coefficients are increased by 0.1 to 0.35, which indicates that the mutual supporting strength between water level and flow in the intersection area is weakened.  (3) In the four operation periods of pre-discharge, discharge, water storage and low flow of the Three Gorges Reservoir, the variation ranges of correlation coefficients of Jianli, Chenglingji, Luoshan during flood diversion and recharge periods are 0.04-0.35 and 0.1-0.39 respectively, the variation ranges of correlation coefficients between pre-discharge period and impoundment period are 0.01-0.1 and 0.005-0.4, respectively. Generally, the strength of hydrological mutual support in the river-lake junction area is weakened.