In view of the status of serious pollution in Lake Taihu basin,it is necessary to establish an appropriate water quality criteria to protect and restore the lake environment.According to the data on total phosphorus,total alkalinity,mean water depth in 12 reservoirs and lakes with little human influence in Lake Taihu basin as well as the early-time (pre-industrial) data in Lake Taihu,a morpho edaphic index (MEI) model was built.The correlations between TP and two factors,which are mean water depth and total alkalinity in MEI model,were analyzed,respectively.Considering the fact that all the lakes in Lake Taihu basin are shallow, the improved MEI model was proposed.Then the improved MEI model was used to determine TP reference concentration in Lake Taihu.The result showed that the reference concentration of TP was 0.025 mg/L.This study is aimed at diversifying the methods of nutrient criteria research in China,and providing theoretic support for eutrophication control in Lake Taihu basin as well as establishing nutrient criteria for similar lakes in the middle and lower reaches of the Yangtze River.s