Through analysing the relationships,between bank-breaching and economy,the authors proposed a method to calculate the sensitivi ty coefficient,and have calculated the sensitivity coefficient of economic damage of flood to each county in the flooded area of lower Huaughe River with the method,further to classify the thirty-two counties into five classes on sensitivity coefficient,which provide a basis for future combatting a flood and going to the rescue in hurry,or changing the channel artificially,also to give a method for future study on economic damage of flood.