Abstract: Using the precipitation data of Dianchi basin from 1970 to 2020 flood period (May to October), data processing by GIS technology, combined with Mann-Kendall rank order test and wavelet analysis etc, we analyzed the trend and periodicity of interannual variation of precipitation, as well as the concentration, concentration period, precipitation center of gravity, evolution of the frequency of droughts and floods in the basin flood period in the past 50a.The results show that: ① in the past 50a, the overall trend of flood precipitation is decreasing, with an increase in precipitation in the central region and a decrease in precipitation in the upper reaches of the Panlong River above the Songhua Dam Reservoir and the southern region; ② there is a 31a main cycle of interannual variation in flood precipitation, with a higher concentration of precipitation in the central main city than in the southern region; ③ the overall trend of the center of gravity of flood precipitation is shifting to the east and south, and the trend of shifting to the east is significant. ④Droughts and floods are frequent in the Dianchi basin, especially in the upper and middle reaches of the Panlong River, which is a drought and flood prone area.This achievement has certain significance for flood and drought disaster prevention and water resources management in Dianchi Lake Basin.