In order to correctly evaluate the trophic state of a lake and then to establish a scientific basis for the prevention of lake eutrophication, a lake eutrophication stochastic assessment method (LESAM) by using empirical frequency curve (EFC) is proposed.In this method, the EFC of each water quality index of an actual lake is firstly derived through establishing the EFCs of each of those water quality indices and assessment orders used in the lake eutrophication assessment criteria.Secondly, the assessment order of lake eutropication is derived by using the weighting average rnethok to calculate the EFC of assessment order of lake eutrophication.The characteristics of LEGAM are that the method is simple, the visual graphs are informative, and the computation work is moderate.LESAM, together with other two methods, i.e.the lake eutrophication (LEGAM), has been tested against the measured data of 30 lakes all over the country, it is found that the difference of assessment results between those three methods is not greater than 1 order in 29 lakes, i.e.96.6% of the total lakes.It is concluded that all these three methods (LESAM, LEFAM, and LEGAM) have comparable computation precision.For there is a lot of uncertainty involved both in determining the number and type of water quality index in lake eutrophication assessment and in determining the assessment order and its corresponding standard water quality concentration, the lake eutrophication assessment methods also have uncertainty.It is suggested that the lake eutrophication assessment should be studied with various approaches in order to overcome the weakness of one particular method and to make assessment results more reasonable.