Objective: To investigate mosquito species composition and density fluctuation in a stable state of urbanization of Wuxi, Jiangsu Province, China, so as to provide a scientific basis for early warning of mosquito-borne infectious diseases. Methods: From March to November of 2012 to 2021, mosquitoes were monitored by lamp trapping in five habitats of urban residential areas, parks, hospitals, rural houses and livestock sheds in Wuxi. The species, densities, and seasonal fluctuations of mosquitoes in different environments were analyzed. An analysis of variance was performed on the similarity and diversity indices of mosquitoes in different years and habitats for annual trends. A linear regression analysis was used to analyze the relationship between mosquito density and the minimum mean temperature in the 5 days before monitoring (T_min⁵), followed by testing with analysis of variance. Results: A total of 3 777 mosquito lamp traps were placed, capturing 27 158 female mosquitoes, with an average density of 0.60 mosquitoes/lamp·h. The dominant species were Culex pipiens pallens/quinquefasciatus and Cx. tritaeniorhynchus. The mosquito density decreased from 1.18 mosquitoes/lamp·h in 2012 to 0.13 mosquitoes/lamp·h in 2021. The seasonal fluctuation of the overall average mosquito density showed a bimodal pattern. The mosquito diversity index of livestock sheds was highest at 0.97, which was statistically higher than that of other habitats (all P < 0.05), followed by rural houses, urban residential areas, parks, and hospitals. There was no statistical difference in the diversity index of different habitats in different years (F=1.328, P=0.253). The similarity index was high between residential areas, parks, hospitals, and rural house but not livestock sheds. In all the years except 2012, mosquito density was linearly correlated with T_min⁵ (all P < 0.05). Conclusions: The species composition of mosquito in different environments in Wuxi is different. The densities of dominant mosquito species in all the habitats showed a generally decreasing trend year by year. The density and diversity of mosquitoes in livestock sheds were highest, which should be a focus of mosquito control. The fluctuation of mosquito density was statistically correlated with temperature, and T_min⁵ can be used as a potential risk indicator for mosquito density surveillance and early warning.