Abstract: The balance of available precipitation is of great significance to water resources, water environment and social development in the water source and water consumption areas of the South-to-North Water Diversion Project. Based on the daily data from 4 weather stations, the available precipitation ranged from 1980 to 2019 in Shiyan city, a typical city located in the water source area of the South-to-North Water Diversion Middle Route Project, was calculated; and the variation characteristics of the available precipitation in the study period were analyzed by Mann-Kendall method and wavelet analysis method. The results show that: due to the slight decrease of precipitation and the obvious increase of potential evapotranspiration in Shiyan city in the past 40 years, the available precipitation shows a decreasing trend(with a tendency rate 42.796 mm/10a). Both the annual and seasonal available precipitation had abrupt changes, and the annual available precipitation had abrupt changes around 1991. The significant quasi-periodicity of annual and seasonal available precipitation in Shiyan city is within 5 years. The available precipitation resources in Shiyan city is increasingly tight, and it is necessary to make full use of foreign water resources, to improve the efficiency of water resources utilization, and to ensure the smooth operation of the water conveyance project of “South-to-North Water Diversion”.