According to Basic Analytical Methods of Environmental Quality Standards for Surface Water in China (GB3838-2002)，we used the 2002-2004 monitoring data to evaluate and characterize water quality condition of Lake Dongting, based on the application of comprehensive index methods such as Nemerow Index and Huangpu River Organic Pollution Index. The results are obtained as follows ： (1 ) The main pollutants of Lake Dongting are total phosphorus (TP)，total nitrogen (TN) and fecal coliform. (2) The mean Huangpu River Organic Pollution Index is 0. 27, indicating that the water quality does not have the black smelly phenomenon at twelve designated sections in Lake Dongting. (3) In western and southern Lake Dongting, the water pollution could be more serious during the drought water season, whereas during the normal water season in western Lake Dongting the water pollution is also bad. The water quality are generally better during the flood water season than those during normal water season. (4) Pollutants make a great contribution to the water quality of Lake Dongting； and the main sources are industrial effluents and domestic sewage. (5) The pollution condition of the main lake are not serious during 2002 -2004, while in certain water areas heavy pollution condition may occur during the drought water season. The investigations suggest that lake water quality has improved in recent years in response to changes in the land restoration of reclaimed areas and the construction of the Three Gorges Project.