Based on the monthly water quality monitoring data of rivers flowing into West Yangcheng Lake from 2007 to 2019, the spatial and temporal variation characteristics of water quality in rivers flowing into West Yangcheng Lake were analyzed. The results show that the rivers flowing into West Yangcheng Lake had the characteristic of high content of nitrogen and phosphorus nutrients in spring. The annual average mass concentration of NH₃-N, TN and permanganate index showed overall downtrend with the decline rate of 78. 7%, 47. 9% and 34. 8% respectively in 2019 compared with 2007. The annual average mass concentration of TN declined considerably after 2015. The annual average value from 2015 to 2019 declined by 45. 3% compared with that from 2007 to 2014. Water quality in Litang River and Baidang were the worst among rivers flowing into West Yangcheng Lake with the main pollution factors of NH₃-N, TP and TN.