Flood risk analysis for the Shisan dyke flood protection zone is very imperative as the zone is located in the Pearl River network area with high flood peak and severe flood threat. Since the water flow in the Pearl River network is complicated, we first of all built a one-dimensional model of the Pearl River network and verified the reliability of the model based on historical flood data. Furthermore, we built a two-dimensional hydrodynamic model of the flood protection zone using a refined unstructured grid to simulate the flood evolution in the purpose of reflecting the impact of rivers, dikes and roads in the protected area on flood propagation. Assuming that dike breach occurred in the Jianggen segment and the Xitoudou segment, we simulated the flood inundation in the Xijiang River under design flood of 50-year event flood, 100-year event flood, and 200-year event flood by coupling the 1D model and 2D model. The rationality of computation results was examined in terms of water balance analysis, local flow field analysis, and water level process at the breach. In association with socio-economic data, the impacts of flood were also investigated from aspects of inundated area, affected population, and inundation losses. Combined with socio-economic data, the flood impact analysis is finished, such as flooded area, affected population, and inundation loss.