Abstract: The Pearl River Basin is a typical subtropical humid region. Its climatic conditions are affected by the alternation of atmospheric systems, such as cyclones/subtropical high pressure, and the complex underlying surface conditions. It is prone to drought and flood disasters, which could seriously threaten Water security in the Pearl River Basin and the Greater Bay Area(Guangdong, Hong Kong and Macao). In order to comprehensively analyze the spatio-temporal evolution trend of drought-flood abrupt alternation in the Pearl River Basin, the intensity, duration, frequency and strength of drought-flood abrupt alternation events were analyzed by using trend test, spatial center of gravity transfer trajectory and other methods based on the hydrometeorological observations of the Pearl River Basin from 1961 to 2020. The results show that although the overall interannual trend of the drought- flood abrupt alternation in the Pearl River Basin is not significant, The characteristics of the drought-flood abrupt alternation in the Pearl River Basin in the past 20 years (2001-2020) have been mitigated significantly compared with 1961- 2000; Spatially, the most serve drought- flood abrupt alternations are mainly concentrated in the upper reaches of the Pearl River Basin, while the middle reaches are less affected by the drought-flood alternation. Moreover, during the period from 1961 to 2020, the characteristics of the flood- to- drought events gradually shifted to the upstream direction of the Xijiang River Basin, and the characteristics of the drought-to-flood abrupt change event showed a trend of transferring towards the downstream direction of the basin.