Zizania latifolia communities are a key wetland vegetation type in Poyang Lake, and their spatial distribution is significantly affected by the hydrological regimes of the lake. Since the water level of Poyang Lake dropped in 2003, the Z. latifolia community has shown an expanding trend, which may have an important impact on the suitable habitats of migratory birds. However, their spatiotemporal dynamic and underlying driving mechanisms remain poorly understood. In this study, we developed a high-accuracy remote sensing extraction model by integrating multi-source data, taking advantage of the phenological characteristics and distinctive winter spectral features of Z. latifolia. We systematically analyzed the spatiotemporal dynamics of Z. latifolia communities in Poyang Lake from 1987 to 2023 and further examined their dominant driving factors. The results revealed that Z. latifolia communities were primarily distributed in the 12–14 m elevation zone of Poyang Lake and in dish-shaped lakes, with mean proportions of 62.9% and 66.2%, respectively, during the study period. From 1987 to 2023, their total area followed a pattern of “initial increase followed by decline”: sparsely distributed before 2003, expanding rapidly thereafter, peaking in 2018 (57.65 km2), and collapsing abruptly after 2020. Since 2003, the decline in water level of Poyang Lake has been significantly correlated with the rapid expansion of the Z. latifolia community, a pattern that indicates the former may be the main driving factor. In contrast, the extreme flood in 2020 and the subsequent frequent drought events were temporally synchronous with the rapid degradation of Z. latifolia communities, indicating that they may be the key environmental factors contributing to the degradation.These findings not only provide valuable data support for understanding the ecological evolution of Poyang Lake wetlands, but also offer important insights for their future conservation and adaptive management.