Xiangjiang River, a main tributary of Dongting Lake water system in the midstream of Yangtze River, is the largest river in Hunan province. Knowing the changing trend of water level in Xiangjiang River can provide support for the protection and management of Xiangjiang River basin and even Dongting Lake. The M-K testing method was used to analyze the water level changes of the downstream of Xiangjiang River from 1990 to 2014, and the riverbed evolution of the downstream of Xiangjiang River was analyzed based on actual-measured topographic data. Meanwhile, the relationship between the riverbed evolution and the water level changes were inspected. The results indicated that the water level showed an overall downward trend from 1990 to 2015. The water level in Changsha, Xiangyin and Yingtian stations all dropped to the lowest level in 2011, which were 26.62 m, 24.69 m and 24.42 m, respectively. The decline of water level was obvious especially during the dry season. From 1990 to 2014, the highest water level of the flood season gradually declined, while the lowest water level gradually decreased as well. Under the same flowing volume, the change of water level was not obvious in flood season but droped in dry season in dry season. From 1983 to 2015, there were two types of typical sections, i.e., horizontal widening and vertical deepening. The riverbed of the downstream of Xiangjiang Rivers was severely incised, which of Tongguan Bar reached to 15.7 m below. The change of water level in flood season was related to incoming water and sand as well as riverbed evolution before, while that in dry season mainly attributed to riverbed undercutting.