Depend on the indices of COD, T-N, PO4-P and chlorophy11-a, the eutrophication in the north of Zhejiang coast was assessed by the method that associated with weighing distance and subordinative degrees of fuzzy set theory. In the course of the assessment, the significance-weighing vector was determined by the modif ied hierarchy analyzing method and the signif icance-compared matrix of the assessment indices was adjusted. The assessment results were given in two ways of subordinative and accumulative methods. The results showed that the area with middle and middle-high eutrophication were 76. 6% of the researched area, while the area with lower and higher than that being 16. 6% and 6. 7% respectively. The different arranges of assessment indices influenced the f inal assessment results, and the accumulative method was of higher exactitude than the subordinative method for describing status of eutrophication. The further research needs to be carried out on the relativity between ertrophication and algae bloom.