Abstract: According to the characteristics of multiattribute decision making, uncertainty and fuzziness during the process of eutrophication assessment, an integrated method is proposed for eutrophication comprehensive evaluation on the basis of multi-element connection number and triangular fuzzy numbers. Multielement connection number is applied to depict the uncertainty of subordinative relationship between the evaluation factors and evaluation grade. The triangular fuzzy numbers are used to express the continuous changing process and fuzziness of difference degree coefficient of connection number. Then, comprehensive connection number between the evaluation factors and grade is calculated, the characteristic value of evaluation grade is determined based on combination weight of the evaluation indexes. Eutrophication status of cascade reservoirs on the Huangbaihe River in July, 2016 was evaluated as a case. The results showed that the eutrophication status of Xuanmiaoguan Reservoir was oligotrophic, and Tianfumiao Reservoir, Xibeikou Reservoir, Shangjiahe Reservoir were all mesotropher. Their eutrophication in the order were Shangjiahe Reservoir> Xibeikou Reservoir > Tianfumiao Reservoir > Xuanmiaoguan Reservoir. Compared with the results from some other widely used methods, the evaluation result in this paper was intuitive, effective and can reflect actually eutrophication status. Meanwhile, different from other methods, it could distinguish accurately internal differences at the same eutrophication level. This method has a good application prospects in assessment of lake and reservoir eutrophication.