Lake is an important water resource. However, a common accepted and reliable synthetic evaluation index for lake water quality is not found. In this study, grey relational analysis were used to evaluate the eutrophic status for the lakes of Yilan Area. Results obtained from grey relational analysis were compared with that obtained from Carlson trophic state index as well. The analysis results indicate that (1) grey relational analysis can be successfully established for eutrophic state evaluation. No mater Deng's formula or Wen's modified formula was applied for the calculation, there is no big difference in the results of eutrophic state classification. (2) In the 5 evaluated lakes (calculated by Wen's modified formula), 4 of them were classified as mesotropic. One lake was classified as mestropic/eutrophic. In general, a better eutrophic status of lake is obtained from grey relational analysis rather than that rated by Carlson trophic state index. (3) Data were normalized or not before grey relational analysis, the outcome of trophic state classification is different in some lakes. Therefore, data pretreatment for grey relation analysis need to be carefully considered. (4) For the evaluation of eutrophic status for lakes, we found that the detection limit of total phosphorus need to be improved to avoid the different rating that caused by data with total phosphorus below detection limit.