In order to explore the variation characteristics of Poyang Lake water level before and after the impoundment of the Three Gorges Reservoir, the hydrological data of Hukou, Xingzi, Duchang, Tangyin and Kangshan Station from 1964 to 2016 were analyzed. The results showed that except for a significant increase in the minimum water level at the Hukou station, the annual maximum water levels, annual minimum and annual average water levels at the remaining four stations, the annual maximum and average annual water levels at Hukou station kept decreasing. The variation amplitude of water level in Poyang Lake was the largest in October and the fluctuation range of dry-water water level decreased from October to March. Except for Hukou Station, the variation amplitude of water level in March was the smallest for other four stations, the variation amplitude of water level in the north is higher than that in the south, the monthly water level change of Xingzi Station was less than that of Duchang Station from December to March next year. The water level of Hukou in the dry season was higher than before the construction of the reservoir. The dry time has prolonged for Poyang Lake and averaged extension was 41 days. The time of appearance of dry water fluctuates in advance.