Abstract: MIKE software was used to construct a flood analysis model for twenty-four polder flood protection area in the lower reaches of Ganjiang River. The model includes one-dimensional river flow coupled with two-dimensional surface hydrodynamic flow. Based on recorded water level and discharge data from May 1, 2010 through September 30 and May 1, 2012 through September 30,flow rate of the one-dimensional model was determined and validated, and the roughness of the twodimensional model was estimated based on existing conditions of the underlying surface. The model was used to simulate the hydrodynamic process of the twenty-four polder area with high flood conditions and embankment breaching scenario. The flood discharge process, water level process, water depth and velocity distributions were simulated. The results show that the model can simulate the flood process with flow rate along the water level fluctuation in the protected area and the distribution characteristics of the depth and velocity in the protected area with good accuracy.