Referring to the different water body function, the survey of water quality was carried out on major urban lakes of Beijing monthly in 2006. According to TLI method, the state was evaluated on the basis of measurement result: lakes of drinking water source were mesotropher; lakes of major landscape water were light-middle eutropher; lakes of ordinary landscape water were middle-hyper eutropher. The eutrophic characteristics and its changing trend were analyzed. The causes were analyzed. The measures and suggestions were expounded on different water body function for improving water quality and reducing eutrophication.