Abstract: The total nitrogen (TN) flux from the Yangtze River into the sea has a significant impact on the water environment and aquatic ecology of the coastal waters.Based on the selected cross-section, TN concentration and flux into the sea of the Yangtze River Estuary from 2005 to 2022 were studied.The results showed that: (1) Annual TN flux fluctuated greatly.The maximum (2.63 million ton/a) flux was 2.7 times of the minimum.The flux showed the trend of first increasing and then decreasing.During 2008 through 2019, fluxes were relatively high with greater 2.00 million ton/a in most years.Since 2016, the yearly TN flux showed an overall downward trend, from 2.63 million ton/a in 2016 to 1.16 million ton/a in 2022.(2) The annual TN flux and runoff fluctuated with the similar rhythm.A higher TN flux was often accompanied with a higher runoff.Comparisons under the condition of similar runoffs, the change of annual TN flux indicated the significant effectiveness in water pollution control.(3) TN concentration in the Yangtze River Estuary was higher during the dry season than during the wet season, with an average increase of 24%; However, TN flux into the sea was significantly higher during the wet season than that during the dry season, and the former was approximately 1.93 times that of latter.(4) During 2016~2022, TN loads from the upper reach of the Yangtze River, Dongting Lake, Han River, and Poyang Lake accounted for 43.8%, 24.4%, 4.9%, and 10.8%, respectively, of the total flux.The net increase in TN load in the mainstem of the middle and lower reaches of the Yangtze (excluding sources from the upstream, Dongting Lake, Han River, and Poyang Lake, i.e.TN loads from other tributaries and those entering directly the mainstem) accounted for 16.2%.