Abstract: This paper analyzed the annual change trend of the monitoring data of Luoshijiang River from 2011 to 2019, and analyzed the annual change of the concentrations of DO, COD_Cr, NH₃-N and TP of three monitoring sections of Luoshijiang River. It showed that the water quality of Luoshijiang River was improving year by year, but the pollution was worse in spring and summer. Based on the analysis of the spatial distribution of four water quality indexes in three sections of Luoshijiang River, it could be seen that the water quality of Shapingqiao section was the best, that of Xichang village section was the second, and that of Lianhe village was the worst. Based on the analysis and study of the temporal and spatial variation characteristics of water quality in Luoshijiang River, this paper provided reference for harnessing the Luoshijiang River, protecting and restoring the water quality function of Erhai Lake.