A catastrophic flood occurred in Changjiang River watershed in 1998. It was not only an exceptionally serious flood with a high level and long continual time, but also resulted in serious calamity. A great attention was paid to by the personalities of various circles in the world. Based on the contributing of the characteristics and process of the inundation this year, the paper discussed the contributing factors. It is considered that the main influent reasons of the flood were the destruction of ecological environment, except the influence of climatic change, and the serious reduction of forest resources, tillage on steep mountain slopes both in the area of upper and middle reaches of the river and the decrease of storage volume of lakes and reservoirs in the down reaches. It is considered that to increase the consciousness of ecological environmental protection, to develop and protect forest resources are the inevitable measures to reduce the influence of flood disasters and realize the territory