Abstract: Aiming at the shortcomings of the single flood risk analysis in the flood protection zone, in this paper the one-dimensional and two-dimensional unsteady flow basic control equations are taken as a theoretical base for analysis of flood risk. In order to solve the discrete grid problem, the finite volume method (FVM) is used for solving discrete grids. A multi-source coupling mathematical model for levee-breach flood and rainstorm has been established at the same time. The 1D and 2D models are jointed through a weir flow equation to calculate the real-time interaction between the river and the flood protection zone. It is optimized by dry depth and wet depth theories for the sake of making faster and better results. And this model has also utilized a remote sensing image interpretation method to deal with the complicated roughness having important impacts on the flood routing. And a generalized method is used to deal with the roads and water culverts which prevent or guide the flowing of water in the flood protection zone. This model is tested by historically measured flood data, which are the basic requirements in actual engineering simulation, and then the verified model is applied to simulate the multi-source flood occurring in the flood protection zone at Fengtai reach. Analysis of the big difference between the serious damages caused by a single flood and a multi-source flood is carried out. The research findings are of great significance in analyzing the multi-source flood and simulating flood motion coupling. And researchers can use the analysis results to make risk evaluation of the flood in the research area and also in some similar flood control protection areas.