Hazard area of rainfall in Tongcheng County on June 10 2011 was analyzed according to runoff equilibrium theory. Flood inundated area was simulated by using GIS flood drowned model based on rainfall and DEM data, and the simulation results was tested and analyzed with the disaster results. The result shows that the whole county was inundated by different degrees, and the inundated areas focus in river and low lying areas. The depth inundated areas is between 0.5 and 2 m, accounting for 35% of all the inundated areas. The siumulated inundated area is similar to the actual situation.