Abstract: As a large floodplain wetland, Poyang Lake is a crucial wintering ground for herbivorous migratory birds. The suitability of its wetland ecosystem is significantly affected by water level fluctuations. Using high-resolution Sentinel-2 images (2017-2022), measured vegetation biomass data, and high-precision topographic data from the lake basin, a Habitat Suitability Index (HSI) was developed based on concealment conditions, food abundance, and forage palatability. The spatiotemporal distribution patterns of habitat suitability were evaluated at a ten-day scale during the wintering period across different hydrological years in the Poyang Lake National Nature Reserve (PLNNR). Furthermore, we analyzed the response of habitat suitability to water level fluctuations, elucidating the impacts of water level dynamics at different wintering stages under varying hydrological years. The results indicated that: (1) The suitable water level range for herbivorous migratory birds in PLNNR was 9.56~11.69 m (Wusong elevation), corresponding to the highest habitat suitability. (2) During normal hydrological years, stable water levels, especially in critical periods (December), significantly enhanced habitat suitability for wintering birds. (3) Water level fluctuations in different stages of normal hydrological years exerted distinct influences on habitat suitability-falling water levels in the early wintering period (September to November) facilitated foraging, while rising water levels (February to March) in the later stages provided stable roosting space. This study underscored the importance of flexible and precise water level management in maintaining habitat suitability for migratory birds. Water level regulation strategies should be adapted to the fluctuation patterns of different hydrological years.