Abstract: A total of 20 samplings site were set in Lake Dongting to measure the concentrations of TOC, TN and TP in the surface sedeiments of the lake. The spatial distribution characteristics of nutrient concentration were analysed, the organic index was used to evaluate the organic pollution level of the sediments, and the source of organic matter in sediments were analysed according to C/N ration and ¹⁵N isotope ratio(δ ¹⁵N). The results showed that the average concentrations of TOC, TN and TP in the surface sediments of Lake Dongting were 13 260, 1 046 and 368.85 mg/kg, respectively. The spatial distributions of different nutrient concentrations were significantly different, but they all showed a decreasing trend from West Lake Dongting to East Lake Dongting and South Lake Dongting. Organic nitrogen pollution existed in 20% of surface sediments of Lake Dongting, but the overall surface sediments were clean to relatively clean, not up to the level of organic pollution. The average C/N ration value of the surface sediments was 13.22, and the organic matter in the sediments was mainly from the exogenous inputs. The analysis of δ ¹⁵N further indicated that organic matter in land soil was the main source of organic pollution in the sediments. It was suggested to strengthen the control of soil organic loss in land areas.