Given ongoing changes in regional climate and hydrologic conditions, a vast of studies have reported that under-prediction or over-prediction of the trophic status of a water body was widely existing by classic trophic state index method, it would create serious problems in management aspects such as allowing over-fertilization of the eutrophic water body. Each lake needs to establish its own trophic state evaluation method. Therefore, based on the concept of lake-specific and segmentation, a new assessment method for lake eutrophication is proposed: a Trophic State Footprint Index (TFI). This method constructed a concise response relationship between the response index (chlorophyll a) and the main cause index (such as total phosphorus and total nitrogen) with segmented data. This method is an improvement over the Modified Trophic State Index method and TFI is simpler, easier to conduct, and more accurate. It has been applied in Dianchi Lake of China and proved to be effective.