The paper analysed the envirnoment characteristics that influenced the flood in the middle and lower reaches of Changjiang River, and revealed the rule of the flood affacted by its environment. It indicated that climate, topography, soil etc. were the natural factors which caused the flood, forest played an important role in anti-flood, water and soil loss increased the frequency and potential threat. At last, the paper discussed several problems, and raised different views. More attention should be given to the quality of ecological environment construction. It wasn’t necessary to return the cultivation land into the lake. The Three Gorger Reservoir was going to play a limited role in fighting the flood of the area.