Abstract: In order to analyze the transmission characteristics of nitrogen, phosphorus and silicon in the middle and lower reaches of the Yangtze river and the contribution of the Dongting Lake, Han River and Poyang Lake to the main stream, water samples were collected from the front of the Three Gorges dam to the estuary along the main stream and the entrances to the Yangtze River of the Dongting Lake, Han River and Poyang Lake in September 2020. Concentrations of nitrogen, phosphorus, silicon were measured, the variation trend of nutrient along the river was analyzed, nutrient flux and contribution of main tributaries were calculated. The results show that the total nitrogen concentration in the middle and lower reaches of the Yangtze River decreases along the river and fluctuates between 1.23 mg/L and 2.32 mg/L, and the proportion of dissolved nitrogen is more than 95%. The concentration of total phosphorus increases along the course and fluctuates between 0.01-0.08 mg/L, mainly in granular form. The dissolved silicon concentration increases sharply at the Hankou section, and the mean value from the front of the Three Gorges Dam to Hankou section is 5.52 mg/L, and the mean value from the Hankou section to estuary is 10.8 mg/L. Fluxes of total nitrogen, total phosphorus and dissolved silicon all increase obviously along the river. The tributary river and lakes contributes a lot to the transport of nutrients in the main stream, among which Dongting Lake contributed the most, contributing 163.2%, 67.9% and 23.6% to the transport fluxes of total nitrogen, total phosphorus and dissolved silicon respectively, but the water quality of the main stream does not change obviously after Dongting Lake enters. The comprehensive trophic level index fluctuates between -12.72% and 7.85% after the Dongting Lake, Han River and Poyang Lake merge into the main stream. This study is helpful to understand the nutrient status of the middle and lower reaches of the Yangtze River and the contribution of the tributary river and lakes to the main stream, and to provide scientific basis for water environmental management in the middle and lower reaches of the Yangtze River.