Abstract: Water energy resources in the upper reaches of the Yangtze river are of great significance for China’s energy development. Studying the hydrological cycle and abrupt change rule of water levels in upper reaches of the Yangtze river can prevent the agricultural losses caused by drought and waterlogging in advance. The linear regression method is used to interpolate and extend the water level data of Qingxichang hydrological station in the upper reaches of Yangtze River. Then, the periodicity and catastrophe characteristics of the water level series in the dry season(Jan. to Mar.）and the rainy season(Jun. to Aug.）from 1890 to 2002 are compared and analyzed by wavelet analysis method and Mann-Kendall method. The results show that: (1）The water level in the dry season was higher from 1890 to 1940 and lower from 1940 to 2002; the water level changed frequently in rainy season and remained low after 1965; （2）The water level in dry season has a 5-8 years interannual periodic variation, and is significant from 1900 to 1950. The main cycle of the water level in the rainy season is the decadal change cycle of about 35 years, and there is a significant annual change cycle of about 8 years from 1940 to 1960; (3）During the dry season, the water level changed from high to low after 1933, it continued to be low after 1940. In the rainy season, the water level changed from high to low after 1957, it decreased more in 1965,the water level decreased significantly by the year 1993 and increased after 1997;（4)The changing trend of the surface rainfall in the upper reaches of Yangtze River is consistent with the changing trend of water level in Qingxichang hydrological station. The East Asian summer monsoon was weak and the climate in the upper reaches of the Yangtze River was wet during the small ice age of Ming and Qing Dynasties, and the water level was high as a whole. In the 1930s and 1940s, the global climate was relatively warm, and the East Asian strong summer wind leads to the rain belt locating partial north, the upper reaches of Yangtze River became drier and turned to have a low water level as a whole.