The invention discloses a method for evaluating lake eutrophication, and relates to evaluation methods of water environment pollution. The method solves the influence on TSI by multiple water qualityparameter measurement during the existing computation of the nutrition condition indexes. The method comprises the following steps: firstly, performing sampling on a lake, so as to obtain a lake waterquality sample; secondly, measuring pH, salinity, water temperature, SD, TN, TP, DOC, Chla and aOACs according to the lake water quality sample; thirdly, ensuring that the measurement of the aOACs comprises measurement of ap and aCDOM; fourthly, back calculating the TSI through the measured aOACs, ensuring that data points are uniformly distributed on the two sides of a regression line, and further performing classification of degrees of evaluating lake eutrophication. The method is simple, can compute a TSI value of a lake through a model by only measuring optical active substance absorptioncoefficients of the lake. The method is applied to the evaluation of lake eutrophication.