Donghaochong Basin is located in Yuexiu District, the centre of Guangzhou City. Through investigation and analysis of the causes of inundation at water points in the river basin and the use of numerical modeling, this paper studied urban basin flood process and obtained flood information with certain reliability and accuracy, providing theoretical reference and scientific basis for decision making concerning disaster relief by related departments. According to the principles of hydrologic hydraulics about the process of urban flood, the SWMM was taken as one-dimensional (1D) model, the two-dimensional (2D) hydrodynamic model was coupled through DLL, and the coupled hydrodynamic model was constructed through the connection of horizontal and vertical direction. The flood model of Donghaochong Basin based on the coupled hydrodynamic model was constructed. Two measured rainfall events were simulated and analyzed, and it turned out that the flood model had good accuracy and reliability in the simulation of 1D drainage system and 2D surface waterlogging. The application of the coupled hydrodynamic model in Donghaochong Basin further proved the rationality and feasibility of the coupling model connection algorithm, showing great application value in urban flood simulation and analysis.