【Abstract】　Objective　To firstly investigate the diversity of mosquitoes in the six lake wetland of the northwestern Yunnan, including Qinghai Lake, Erhai Lake, Xihu Lake, Cibi Lake, Jianhu Lake and Caohai Lake.  Methods　During August of 2007 and 2008, adult mosquitoes were caught with UV light?traps in the Lakes or some villages near to lakes and analyzed.  Results　A total of 215 707 adult mosquitoes were collected and identified belonging to 2 subfamilies, 19 species and 5 genera.  Among them, Culex tritaeniorhychus was the dominant species (85.54%), and Anopheles sinensis was common species (10.95%). The statistical results suggested:  (1) The species of mosquitoes from Cibi Lake and Jianhu Lake were the most abundant, that from Xihu Lake and Caohai Lake was second. That from the Erhai Lake and Qinghai Lake was the minimum. From south to north, the species richness presents increase tendency. (2) Shannon?Wiener index and Pielou index in Cibi Lake and Caohai Lake were the highest, the second was Xihu Lake and Jianhu Lake. That in Erhai Lake and Qinghai Lake was the minimum. From south to north, the species diversity(H′) of mosquito showed an increase tendency, but the density(D) showed decrease tendency. The two distribution curve showed a negative correlation. Conclusion　Species diversity and density of mosquito showed a negative correlation in lake wetland, and Cx.tritaeniorhychus, as dominant species, leaded the changing tendency of the diversity of mosquito.  In addition, many factors such as species diversity, evenness and ecological dominance reflected the effect of artificial factors on lake wetlands and environment.