The evaluation of eutrophication or trophic state of a lake is in fact a multivariate comprehensive decision-making process quantifying the qualitative problem. Therefore, we should use a comprehensive method to assess lake eutrophication. On the basis of summarizing some comprehensive methods for assessing lake eutrophication reported in China and abroad, it is pointed out that the trophic state index (TSI) should be a major method for evaluating lake eutrophication, since it could provide a continuous numerical class of lake trophic state and a rigorous foundation of quantitative studies of eutrophication mechanism. Using analytic hierarchy process (AHP) to determine the weight attributions in the selected comprehensive indices, the authors, constructed a comprehensive assessment model as: TSI = W(Chla) x TSI(Chla) + W(Sd) x TSI(Sd) + W(TP) x TSI (TP) or TSIM = W (Chla) x TSIM(Chla) + W(Sd) x TSIM(Sd) + W(TP) x SIM(TP) where W(X) were the weights for the above three parameters with value in percentage as 54.0, 29.7 and 16.3, respectively. Additionally, the relations between comprehensive evaluation and other statistical methods such as cluster analysis were briefly discussed.