Abstract: Based on the online and offline daily monitoring data of seven sites in Changsha City in 2020, the chemical component pollution characteristics of PM_2.5 were analyzed.The positive matrix factorization (PMF) model was used to analyze the source apportionments of PM_2.5.The results show that the water-soluble ions in PM_2.5 has the highest mass proportion, accounting for 64.3%, followed by organic matter (OM), accounting for 26.6%, SO₄^2-, NO₃^- and NH₄⁺ are the main components in water-soluble ions.The PMF model identified five sources of PM_2.5, vehicle exhaust emission source (36%), secondary formation source (31%), industrial emission source (16%), biomass burning source (9%), and dust source (8%).The highest proportion at Changsha Environmental Protection College are secondary formation and motor vehicle emissions, reaching 38% and 37%; the contribution of motor vehicle emissions at Mapoling site is the highest, 42%; the sharing rates of secondary formation, motor vehicle emissions, and industrial emissions at Environmental Protection Bureau of the High-tech Zone are relatively similar, 28%, 26%, and 25%.In order to further control PM_2.5 pollution, it is recommended that Changsha could focus on controlling vehicle exhaust emissions, accelerating the elimination of old motor vehicles, and promoting the electrification of fuel vehicles; meanwhile, differentiated control measures should be implemented for different seasons, with focus on controlling vehicle exhaust emissions in autumn and winter; in summer, it is recommended to prioritize controlling oxidants such as ozone to reduce the secondary formation rate of PM_2.5.