Eeutrophication of lakes and reservoirs is the result of nourishing materials imported, which has an effect on water quality.It makes water plant and seaweed overgrowing, and is followed by a series of changing of water quality, deteriorating of water quality, and changing of many water functions.The factors of polluting lakes and reservoirs are increased continuously as the development of social economic construction grows fast and human activities becomes great in numbers in the regions of lake and reservoirs, which may make the eutrophication of lakes and reservoirs very heavy.It is important to reinforce administration of lakes and reservoirs and to treat pollution in the way of comprehensive system.According to the data of water qualities for some main lakes and reservoirs that have been monitored in recent years, we used Principal Component Analysis and Cluster Analysis to classify the lakes and reservoirs into six types, and also study water quality features and application functions for each type of lakes and reservoirs.The assessment method of eutrophication degree was used to assess the degree of eutrophication of some main lakes and reservoirs in Jilin Province, based on six factors of Chla,TP,TN, COD_Mn,BOD₅ and NO₂-N.We also suggested the practical program of lake and reservoir protection for all of six types of lakes and reservoirs.It is very important for the development of regional resources of water, for assessment and prediction of environment quality and for the plans of controling eutrophication of lakes and reservoirs.