From 1984 to 1986, based on the knowledge of the present condition and characteristics of avian resources in the Three-Gorge Reservoir area, we investigated the change of the avian distribution and community composition in other areas where dams had been built. After studying and analysing quantiatively every factor of the impact of the Three-Gorge Project on the avian community and species by means of biometrics, we give a quantitative and qualitative evaluation.The results indicate that the construction of the Three-Gorge Reservoir will change the avian community composition and bird species distribution in this region. On one hand, the numbers of rare and economic birds, especially the forest birds, which have already become scare in the past ten years, will decrease seriously. On the other hand, the numbers of water birds will increase. In a word, in building the dam, the disadvantages derived from it far outweigh the advantages it brings about.The impacts af a higher dam (180m) and a lower one (150m) on avian community are different. The impact value of a higher dam to the forest and field birds is 30 per cent larger than that of a lower dam, and the impact value of a higher dam to the acuatic birds is two times that of a lower dam.