Drought–flood abrupt alternation (DFAA) is one of the remarkable manifestations of the summermonsoon anomaly at the subseasonal scale and can result in severe damage. This study identifiedand analyzed DFAA in terms of streamflow in the Poyang Lake catchment over the last 50 yearsbased on a DFAA index (DFAAI). The study also investigated the intra-annual distributioncharacteristics and long-term tendencies associated with DFAA, as well as the relationship withprecipitation patterns. A statistical analysis showed that drought-to-flood events in the Poyang Lakecatchment generally occur in March and April, whileflood-to-drought events occur in July andAugust. A Mann–Kendall test indicated a long-term decreasing trend inDFAAIin March and April anda slight increasing trend in July and August; however, the trends were not statistically significant.Flood-to-drought events occurred more frequently than did drought-to-flood events at the decadalscale, especially in the 1960s and 1970s. The particular distribution of precipitation in the PoyangLake catchment mainly determined the occurrence patterns of DFAA events, but intensive humanactivities are also significant factors that have decreased and mitigated DFAA disasters since the1980s in the Poyang Lake ca