Recently, there is an increasing number of incidents, indicating that cities are suffering more from extreme weather events like typhoon and rainstorm. However some cities are still lacking of the protection of severe weather due to the climate change. It seems that the standard of hazard protection may be inadequate with the change of climate in the future, facilities like low voltage substations and distribution equipment may have a higher chance to breakdown during flooding events. Based on hydrodynamic theory, rainfall is assumed to be the main source of flooding. High resolution geographic information data and GIS grid analyzing technology based on FloodArea model are applied to make flooding simulation and calculation for flood disaster caused by rainfall in Taizhou area. And then the flooding area and depth of water of different rainfall scenes are simulated. Finally, combined the information distribution of disaster-bearing bodies of 10 kV electric distribution network, the critical rainfall to distribution network equipment under different levels causing disaster is determined.