The uncertainty of index system was descried using
　　membership function, and the knowledge information in
　　index
　　membership about object elassifieation was studied. A
　　comprehensive evaluation model of unascertained
　　measurement was
　　established according to the analysis of contribution
　　of index to sample classification and the conversion
　　method of membership
　　degree from index to sample. The results indicate
　　that this model can be used to evaluate the
　　environmental effect of water
　　conservancy and hydropower development of nujiang.