In this paper, a distributed catchment-hydrology model and a physically based lake hydrodynamic model were used to simulate the large-scale and highly dynamic lake catchment system of Poyang Lake, in the middle reach of the Yangtze River basin, China. The simulation of the hydrodynamics of the lake is a significant extension to previous efforts to simulate Poyang Lake's considerable variability in lake extent and flow rates. Further, the combination of the distributed catchment-hydrology model and the lake-hydrodynamic model, applied to a highly dynamic and large-scale system, is a rare attempt to develop a physically based management model of this complexity and scale. Model calibration and validation were undertaken to evaluate the model's performance and to enhance its effectiveness in simulating catchment discharges, lake water levels, lake water surface areas, and lake flow patterns. The results showed a satisfactory agreement with field observations, with Nash-Sutcliffe efficiencies of 0.71-0.84 for catchment discharges, 0.88-0.98 for lake water levels, and 0.80 for lake outflows during the calibration period. The Nash-Sutcliffe efficiency values for the validation period, ranging from 0.62 to 0.97, were largely consistent with the calibration values. Further investigation of the results showed that the modeling approach simulated adequately the lake hydrodynamics in terms of the flow fields within the lake and the seasonal changes in the lake water surface area. The outcomes of this paper will benefit future modeling efforts by providing a tool for predicting the hydrology of Poyang Lake and its catchment under climate variability and land-use changes.