The hydraulic characteristics at the confluence reach of river and lake are influenced by multiple factors such as inflow,topography and vegetation resistance,and are very complicated.In this article,the confluence reach of Yangtze River and Dong-ting Lake is selected as a special example and a hybrid model is built to study the flow at this confluence,with the consideration of the interactions between aquatic vegetation and flow.Validation tests and calculations show that the model is effective and highly accurate.The simulations show that the separation levee at the confluence reach may change the discharge capacity in the flood plain,which would be enhanced in the upper reach of the levee,hardly changed in the middle reach and reduced at the lower place.Moreover,the separation levee also limits the water exchange between the Yangtze River and Dong-ting Lake. The hydraulic characteristics at the confluence reach of river and lake are influenced by multiple factors such as inflow, topography and vegetation resistance, and are very complicated. In this article, the confluence reach of Yangtze River and Dong-ting Lake is selected as a special example and a hybrid model is built to study the flow at this confluence, with the consideration of the interactions between aquatic vegetation and flow. Control tests and calculations show that the model is effective and highly accurate.The simulations show that the separation levee at the confluence reach may change the discharge capacity in the flood plain, which would be enhanced in the upper reach of the levee, hardly changed in the middle reach and reduced at the lower place .Moreover, the separation levee also limits the water exchange between the Yangtze River and Dong-ting Lake.