Abstract: The Tuojiang River is an important inflow river and the primary sources of total phosphorus (TP) in the upper reaches of the Three Gorges Reservoir. The study on the spatio-temporal variation characteristics and causes of TP concentrations in Tuojiang River Basin is important for the up-to-standard control of allowable throughput of TP in the Three Gorges Reservoir and the control of TP pollution in the basin. Based on the water quality data of 20 national and provincial monitoring sections of the trunk and tributaries in Tuojiang River Basin and pollution source data in the confluence area, the spatio-temporal distribution characteristics and influencing factors of TP concentrations in Tuojiang River Basin were comprehensively analyzed, using statistical methods, including correlation analysis, single factor analysis, and hierarchical cluster analysis. The results showed that from 2011 to 2018, the pollution of TP in Tuojiang River Basin had spread from the upper reaches of Mianyuan River, Shiting River, Duck River and the middle reach of Fuxi River to the entire basin. TP in the upper mainstream of Tuojiang River was primarily affected by the inflow of tributaries with serious TP pollution. TP concentrations increased continuously along the mainstream of Tuojiang River and reached the maximum in Sanhuangmiao section with (0.251±0.213) mg/L. TP concentrations floated in the middle and downstream reaches with concentration peaks occurred at sections of Yinshanzhen ((0.194±0.048) mg/L) and Damozi ((0.232±0.057) mg/L). TP concentrations in the flood seasons were higher than those in the dry seasons. The differences of TP concentrations between the flood and the dry seasons were significant with P<0.05. Non-point sources pollution contributed more on TP in Neijiang, Zigong, and Luzhou sections in the middle and lower reaches of Tuojiang River Basin. Point sources discharges mainly affected TP concentrations in Chengdu and Ziyang sections of the upstream trunk stream and tributaries in Neijiang and Zigong.