Understanding the hydrological relationship and its variation in the Changjiang River and Lake Dongting confluence reach is important for the flood control safety of the middle and lower reaches of Changjiang River. Using the M-K mutation test and Morlet wavelet transform methods, this paper analyses the hydrological data (daily water level and flow data) of Chenglingji, Luoshan and Jianli in the past 100 years. We examine the hydrological characteristics of the confluence reach, including annual distribution, interannual variation, variation trend, catastrophe characteristics and variation period, and the specific causes are also discussed. We find that: (1) the maximum water level of the confluence reach usually occurs in July, and the minimum water level occurs in January or February; (2)The annual runoff is mainly concentrated from May to September, with the proportion about 63.64%-73.44% of the whole year; (3) The Chenglingji water level rises as a whole in the recent 50 years (1968-2017), and the high, middle and low rise 0.98, 0.56 and 1.46 m, respectively; (4)The annual runoff ratio of Chenglingji and Jianli Stations decreased to 0.66 in the recent ten years; (5)The cutting and straightening in the 1970s and the impounding 175 m of the Three Gorges in 2008 has obvious influence on the hydrological characteristics over the years; (6)The annual runoff and water level's average period is about 16 a in the Chenglingji and Luoshan Stations, and Jianli Station is about 8 a; (7) From 1954 to 2017, the maximum value of discharge ratio has been decreasing, and its occurrence time is gradually advanced. The results provide a scientific reference for the further study of the complex river and lake evolution in the river basin.