Abstract：Due to the seasonal changes of hydrologic connectivity between the main lake and the seasonal lakes of Poyang Lake, the inconsistent characteristics of inundation conditions in both are remarkably obvious, leading to their different habitat. Based on the reconstructed high spatial-temporal resolution inundation dataset of the Poyang Lake from 2000 to 2020 by adopting the ESTARFM model (Enhanced Spatial and Temporal Adaptive reflection fusion model), this study explored the spatio-temporal variation and the driving factors of inundation dynamics in the Poyang Lake-floodplain system. The results show that the mean value of the inundation area in the main lake and the seasonal lakes are 1232 km2 and 392 km2 respectively. The inundation of seasonal lakes in the floodplain area varies significantly in March and October due to the natural process of lake inundation and anthropogenic disturbance. Generally, the spatial distribution of inundation frequency of Poyang Lake decreases from north to south with the inundation frequency in the regions of the main lake and seasonal lakes are of 58% and 36%, and the mean value of 49%. During the study period, the inundation area and inundation frequency of the entire Poyang Lake-floodplain system showed a decreasing trend, while a slight increasing trend was observed for both of the variables in the seasonal lake region. The inundation dynamics in the Poyang Lake-floodplain system is mainly controlled by changes of the catchment inflow, the stage of Yangtze River and the topography of the lake basin. In recent years, the increase of catchment inflow is the main reason for the increasing trend of the inundation area and inundation frequency in the seasonal lake region. However, the decrease of inundation area and inundation frequency in the main lake area is mainly attributed to the increase of the lake outflow capacity caused by the compounding factors of decreasing streamflow from the upper-middle Yangtze River, the riverbed lowering in the middle-lower Yangtze River due to Three Gorges project operation, and the down-cutting of outflow water channel due to large-scale sand mining activities in the lake. The research results have important scientific significance for deepening the understanding of hydrological complexity of lake-floodplain system and promoting the management practice of floodplain wetland system.