Phosphorus is a pollutant of major concern in the Yangtze River basin. The Wujiang River is one of the eight major tributaries of the Yangtze River, and its mouth is downstream of the tail of the Three Gorges Reservoir. The Wulong section is the control section of the Wujiang River entering the Yangtze River. The interannual changes and seasonality of discharge, and the concentration and flux of suspended sediment (SS) and P (including total phosphorus (TP), dissolved phosphorus (DP) and particulate phosphorus (PP)) at the Wulong section from 1998 to 2019 were studied. Based on the principle of river base flow segmentation, P loads from point and non-point sources were analyzed. The results showed that from 1998 to 2019, the discharge fluctuated up and down within a certain range, while the SS concentration and flux decreased sharply. (2) Over the past 22 years, the concentration and flux of TP and DP have shown an overall trend of increasing and then decreasing. Exceptionally high TP and DP concentrations and fluxes were observed during 2009-2013, the so-called peak P pollution period. (3) 2007 was an important time node, before which P was mainly in particulate form, with an average percentage of 65% of TP, and after the node P became mainly in dissolved form, with an average percentage of 84% of TP. The variation in water and sediment conditions was the main reason for the significant change in P form, and the degree of P pollution was another influencing factor. (4) There was a significant difference in the seasonal distribution of P flux compared to before, showing a decrease in the wet season and an increase in the dry season. (5) The percentage of point source load in the period 1998-2012, 2009-2013 and 2014-2019 was 23.5%, 36.8% and 62.1% respectively, indicating an increasing trend. (6) It is recommended to set appropriate TP control targets, pay close attention to existing P pollution risk points, and strengthen monitoring and source control.