Abstract: The distribution and change characteristics of SO_2, CO, PM_2.5, PM₁₀, NO₂ and O₃ air pollutants in Mile City of Yunnan Province were comprehensively analyzed, based on the mass concentration data of major air pollutants and the meteorological data of Global Data Assimilation System (GDAS) in Mile from 2017 to 2022, and the contribution of different regions to the concentration of PM_2.5, PM_10, O₃ in air of Mile was studied, by using the clustering method, weighted potential source contribution factor method, and weighted concentration trajectory analysis method. The results show that: ① the main air pollutants in Mile City are O₃, PM₁₀ and PM_2.5. The pollutants are concentrated from January through May; the air quality is obviously improved in the rainy season; the obvious pollution period is from winter through spring; and O₃ concentration peaks appear in April and August every year. ② The daily variation characteristics of pollutants are obvious; the concentration of O₃ in air reaches its maximum between 16:00 and 18:00; and meanwhile the concentration of NO₂ reaches its minimum, opposite to that of O₃. Besides, the daily variation of SO₂, NO₂ and O₃ concentrations is in air unimodal, while the daily variation of CO, PM_2.5 and PM₁₀ concentrations is multi-modal. ③ The polluted air masses from the areas to Mile City’s southwest, south, southeast, northeast and east greatly contribute to the ambient air pollutants of the city, with the majority of pollutants coming from the southwest areas. In other words, the northern parts of the three countries, Myanmar, Laos and Vietnam, are the potential source areas of fine particles in air in spring and winter of Mile City.