Abstract: A simplified method of wave current and weir flow intersection from the experiences of several dam-breaks was used to simulate the flood discharges from the Ganhe river during the dam-break on July 14, 2010.Flood routing of the dam-break was simulated by using GIS flood drowned model based on the flood discharges and DEM data.The simulation results was tested by using disaster result analysis.The result shows that the inundated areas of Ganhe river basin were constantly increasing with flood routing, especially for the 0.5~1 meters depth section of the inundated areas.The flood arrived in Renwo viliage at 18:00 on the 14th, then flooded to Maqiao and Yanzhou viliage at 20:00 and 22:00.According to the disaster investigation, in both the aspects of flooding time and flooding location, the simulation result of rainstorm inundation model agrees with the fact.This indicates that the model can better simulate the flood evolution of dam-breaks.