Abstract: On the basis of the water quality monitoring data from 2004 to 2023 of the Daojieba section in middle and lower reaches of Nujiang River trunk stream, DO,NH₃-N,CODmn,and TP were analyzed using single-factor standard comparison evaluation method, linear regression analysis method, and seasonal Kendall test method. The results showed that the general water quality was good. The compliance rate of ClassⅡwater quality throughout the year was 95%. The compliance rate of rainy season was 75%. The compliance rate of non-rainy season was 100%. Each index maintained stable. The concentration of TP demonstrated decreasing change, which indicated that TP was becoming better and better as time went by. There were no obvious changes for other indicators.It would provide references for water resources management and water ecological environment protection for Nujiang River.