Abstract: The Yunnan southern urban agglomeration is a high-risk area for environmental air pollution in Yunnan Province. To clarify the status of environmental air quality and the causes of pollution in the sub-region, the paper analysed the ambient air monitoring data from 2021 to 2022, the results showed that the overall atmospheric environment quality of the southern Yunnan urban agglomeration remained excellent, with an excellent rate ranged from 96.7% to 100%. The pollution periods were concentrated in March and April, with fine particulate matter as the primary pollutant. During the study period, the spatial and temporal distribution of Aerosol Optical Depth(AOD) was highly consistent with the distribution of fire points in the urban agglomeration of southern Yunnan Province and the countries of the Indo-China Peninsula. Backward trajectory analysis showed that during typical pollution processes, the air masses of the five prefectures and cities were mainly dominated by southwest airflow from Myanmar. In summary, the transport of pollutants from the southwest direction was the main reason for PM_2.5 pollution in the southern Yunnan urban agglomeration.