Abstract: The nitrogen and phosphorus flux from the Three Gorges Reservoir (TGR) has a significant impact on the water environment and aquatic ecology in the middle and lower reaches.The changes in nitrogen and phosphorus concentration and flux in the effluent of the Three Gorges Reservoir from 1998 to 2023 as well as the regional source characteristics were studied.The results indicated that: ① From 1998 to 2023, the total nitrogen (TN) concentration and flux in the effluent of TGR showed a trend of first increasing and then decreasing.② From 1998 to 2002 (the pre-TGR operation period), the interannual fluctuations in total phosphorus (TP) concentration and flux were stronger than those in TN, and the concentration and flux of TP in the effluent of TGR were relatively high and fluctuated greatly between years.From 2006 to 2023, they showed a trend of first rising and then falling, especially after 2019 the decrease was more significant.The TP annual flux in 2021~2023 (23, 840 t/a) was only 26% of that in 1998~2002 (91, 470 t/a).③ The construction of TGR and the cascade reservoirs in the lower reaches of the Jinsha River resulted in a significant decrease in the concentration and flux of particulate phosphorus (PP).From 2021 to 2023, the average concentration of PP (0.016 mg/L) was only 13% of that in the period 1998~2002 (0.120 mg/L), and the annual flux of PP (0.716 million t/a) was only 11% of that in the period 1998~2002 (6.635 million t/a).The phosphorus in the effluent of TGR has been transformed from a mainly particulate state before reservoir formation to a mainly dissolved state at present.④ The concentration and annual flux of dissolved phosphorus (DP) in the effluent of TGR reached their peak in 2014 (0.116 mg/L, 475, 700 t/a), and then significantly decreased.⑤ The concentrations and fluxes of TP, PP and DP in the effluent of TGR were significantly higher during wet seasons than that during dry seasons.The TN flux was significantly higher during wet seasons than that during dry seasons, and the seasonal variation of TN concentration was less than that of TP.⑥ The fluctuation rhythm of annual N and P flux was similar to that of annual runoff, but not completely consistent yet.⑦ The N and P load in TGR mainly comes from the upper reaches of the Changjiang River, followed by the Jialing River and the Wujiang River.The N and P pollution in two tributaries of Maoping Creek and Gaojia Creek at downstream of the TGR area is still severe, so it is recommended to carry out small-scale watershed system pollution control.