Abstract: To analyze the composition characteristics and sources of atmospheric particulate matter with different particle sizes in Ili Valley Urban Agglomeration, PM_2.5 and PM₁₀ samples were collected at six sampling sites in four cities/counties, including Yining City, Yining County, Qapqal Xibe Autonomous County and Huocheng County from July 19 to 29, 2021. The chemical components, including elements, ions and carbon components, of these samples were analyzed, and the chemical mass balance model was used to analyze their sources. The results showed that the concentrations of PM_2.5 and PM₁₀ in the urban agglomeration in Ili Valley core area were at low levels during the sampling period, which were (22.81±2.79) and (58.81±6.95) μg/m³, respectively. Among the four cities/counties, the concentrations in Yining City and Yining County were higher than those in Huocheng County and Qapqal Xibe Autonomous County. The results of chemical mass closure analysis showed that mineral dust was the main component of PM_2.5 and PM₁₀ during the study, accounting for 39.8% and 54.1%, respectively. Organic matter was the next, accounting for 33.2% and 19.8%, respectively. Secondary inorganic ions also accounted for 20.2% and 10.7% of PM_2.5 and PM₁₀, respectively. The result of sources apportionment by chemical mass balance model showed that PM_2.5 was mainly contributed by secondary particulate matter (29.1%), dust sources (28.3%), industrial sources (16.1%), motor vehicles (10.5%) and coal combustion sources (9.3%), and PM₁₀ by dust sources (42.3%), secondary particulate matter (14.7%), industrial sources (14.1%), motor vehicles (8.4%) and coal combustion sources (7.3%).