Abstract: Through summarization and comparison of the pollution sources of Taihu Lake, we determined four sources: industry, agriculture, sewage, and rain. Sixteen samples from both lake area and tributary area were collected, and δ¹⁵N and 和δ¹⁸O in these samples were measured. The contribution ratio of pollution sources was analyzed based on the stable isotope technique in association with the model of isotope conservation of mass. Results show that pollutions from industry and agriculture are more serious than those from sewage and rain. As for the samples into the lake from tributary area, the proportion of industrial pollution is basically higher than that of agricultural pollution, and the result of samples from relatively closed lake area is similar, whereas for samples from relatively broad lake area, the result is reverse. On the basis of rationally classifying water pollution resources, quantitative study using isotope technique and numerical model could provide reference for the harnessing of pollution sources of lake. It is also an important approach of determining pollution sources for lake water and pollution conditions.