The operation of the Three-Gorges-Dam (TGD) influences the relationship between Yangtze River and Poyang Lake. In this paper, the river-lake interaction is studied based on Chaos theory. The feature for the flow-sediment and evolution trend after the operation of the TGD is also discussed. In Chaos Theory, the saturated correlation coefficient of the time series represents the complexity of the dynamic system. The saturated correlation coefficient of the discharge time series decreases, while that of sediment transport rate increases. It means the operation of TGD regulates the exchange of the flow and complicates the sediment transport. The saturated correlation coefficient of the selected gauging station in Poyang Lake increases, meaning the regulation of the TGD complicates the change process of the water level. The influence of the TGD for Poyang Lake decreases from North to South.