Abstract: As important water sources in the Erhai Basin, the three northern lakes(Eryuan West Lake, Cibi Lake, and Haixihai Lake) provide abundant water replenishment, which is significant for maintaining the ecological balance and water quality stability of the basin. To clarify the water quality status and eutrophication characteristics of these lakes, this study analyzed water quality categories and trophic state indices based on monitoring data from 2024. The results showed that:① There were significant differences among the three lakes in total nitrogen(TN), ammonia nitrogen(, total phosphorus(TP), chlorophyll a(Chl-a), transparency(SD), chemical oxygen demand(COD), and permanganate index(CODMn)(P< 0.05), while seasonal differences were not significant;② Haixihai Lake and Cibi Lake exhibited relatively better water quality, classified as oligotrophic and mesotrophic, respectively, whereas Eryuan West Lake showed relatively poorer quality, classified as light eutrophic;③Mental-test analysis indicated that the light eutrophication in Eryuan West Lake was primarily influenced by water temperature, TN, N₄⁺ and turbidity. This analysis of the current water quality and eutrophication status provides a scientific basis for comprehensive water quality management and biodiversity conservation in the Erhai Basin.