In order to understand the status of TP pollution of water body in Dongting Lake in dry season,the paper used the (MODIS) data and measured TP data to conducted correlation analysis. The research indicated that the best band combination is b1-b5. The paper set up a cubic polynomial model for retrieval of TP concentration. Furthermore, It obtained TP concentration map at Dongting lake area in 2005, 2009 and 2013 by use of model retrieval. Results showed that TP concentration in most area of Dongting Lake belong to class Ⅳ and class Ⅴ. Finally, the trophic state index model (TSIM) was used to make eutrophication map of Dongting lake. Results suggest that the nutritional status of Dongting lake tends to eutrophication. The trophic index of water body in Dongting Lake dropped slightly and then rose from 2005 to 2013. The most serious area of eutrophication is the east of Dongting Lake, then the south of Dongting Lake, the west of Dongting Lake is relatively the best one. The water quality in inner lake are inferior to that near the outlets of four tributaries.