Abstract: In order to explore the interaction relationship between vegetation and water flow,a two-dimensional shallow water mathematical model was established based on the Godunov finite volume method in the old channel of Fuhe River in Ganfu Plain irrigated area of Jiangxi Province. The flow process was simulated numerically by setting the high flow and level flow conditions,as well as the flood diversion flow of200 m3/s and 400 m3/s under the high flow conditions. The results show that the resistance of vegetation to river flow increases with the increase of upstream inflow,and the extent and extent of its influence on water level also increases,but the effect of water level uplift decreases gradually from upstream to downstream. At the same time,the flow velocity of each section of the river generally increases with the increase of upstream inflow,and the difference of the flow velocity of the vegetated area corresponding to the non-vegetated area also expands further. The flow velocity of the main channel decreases while that of the side bank increases under the condition of no flood diversion.However,it shows the opposite change rule under the condition of flood diversion.Vegetation has an adjustment effect on the flow velocity of the river section,and the channel-bank distributary ratio changes significantly with the change of flow. The above research conclusions can provide important theoretical basis for the analysis of river flood discharge capacity and riverbed evolution,habitat assessment of aquatic organisms and protection of river ecosystem.