Abstract: Frequent extreme droughts have intensified hydrological variability in floodplain wetlands, posing a severe threat for migratory birds. Poyang Lake, the largest freshwater lake in China, experienced an unprecedented extreme drought in 2022, characterized by early exposure of floodplains and persistent dry conditions during the wintering period. However, how such extreme events alter wetland habitat conditions remains poorly understood. In this study, we quantified wetland vegetation conditions relevant to herbivorous waterbird habitats in the Poyang Lake National Nature Reserve by characterizing vegetation structure and potential food availability using fractional vegetation cover (FVC), aboveground biomass (AGB), and normalized difference vegetation index (NDVI). Sentinel-2 imagery (2017–2022) and field-based AGB measurements were integrated to capture habitat dynamics at a 10-day scale across normal-flow (NF), low-flow (LF), and extreme low-flow (ELF) years. Results showed that during NF years, declining water levels exerted strong control on vegetation development, resulting in a progressive expansion of intermediate and high FVC, AGB, and NDVI areas from lake margins toward the central sub-lakes. In contrast, during LF and ELF years, the hydrological-vegetation coupling weakened markedly. The ELF year exhibited abnormally high FVC and AGB during the early wintering period, followed by significant declines in high AGB and NDVI classes as prolonged low-water conditions persisted. This study reveals how extreme drought reshapes wetland vegetation and alters habitat conditions relevant to herbivorous waterbirds, providing insights for adaptive water management and conservation of floodplain wetlands under hydrological extremes.