Abstract：Based on the characteristics of various uncertainties coexist or cross-existence of lake water environment system, extended blind number theories were applied to the field of lake eutrophication assessment. Connecting the extended blind numbers represented the concentrations of parameters with the comprehensive nutrition state index model, the comprehensive trophic level index model was established on the basis of extended blind number theory. Then it was used to evaluate the eutrophication state of Dongting lake. The results showed that the mesotropher region was in the west, south and export of Dongting lake. However, the east Dongting lake were higher, ranging from mesotropher level to light eutrophic level, and had the tendency to the level of meso-eutrophic. Compared with the deterministic method, the comprehensive evaluation model can calculate both the possible ranges and their credible degrees of the comprehensive nutrition state index. Therefore, this model gave a better characterization of the actual eutrophication status and spatial distribution difference of the nutrients which was more scientific and comprehensive.
