Flood disaster is the most frequently and most widely distributed natural disaster in Jiangxi province, particularly in the tail channel of Ganjiang River and Fuhe River influenced by flood coming from the upstream and backwatering effect of the Poyang Lake. Thus, studying flood risk is imperative for improving flood control and disaster reduction capacity, as well as relieving and refraining from loss of life and property. With the flood control area of Fudong dike as a case study, we built 1D-and-2D coupled model in MIKE software to analyze the flood routing process, submerged area and submergence loss under the condition of floods above (50-year event) and below (20-year event) standard together with the backwatering effect of Poyang Lake in different breaches. Results implied that flood risk at different breaches varied due to topographic relief. The flood risk of downstream side breach at Lijiadu hydrometric station is the largest.