Abstract: Based on the daily air pollution monitoring data at the Haikou station from 2013 to 2016 provided by the Hainan Provincial Academy of Environmental Sciences,we analyzed the air quality status in this region.We also explored the major transport paths and potential source areas of the primary air pollutants (PM_2.5 and O₃) throughout December in 2013 using the methods of HYSPLIT trajectory clustering analysis,potential sources contribution factors,and trajectory analysis of concentration weight,based on the upper- and lower-level atmospheric circulation,air quality index (AQI),and aerosol thickness blue images from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite.The results showed that the change in wind direction during winter and summer monsoon is the most important meteorological cause of air pollution in Haikou.The primary air pollutant is PM_2.5,followed by PM₁₀ and O₃.Air quality above the good level reaches a rate of 97.1% in Haikou.The AQI exhibits a decreasing trend year after year,while O₃ increases steadily.Air pollutant concentrations are affectedc by pollutant emissions and circulation fields.In Haikou,air pollution mainly occurs in the presence of three synoptic types,including the cold and high pressure,warming ridges,and typhoon peripheral descending airflow.The long-range transport of air pollutants is the main reason for the occurrence of a typical air pollution event.During this event,the potential source areas of primary air pollutant PM_2.5 are distributed at the junctions of Hu'nan and Jiangxi provinces,coastlands in Guangdong province,the northern part of Guangxi province,the junctions of Jiangxi and Fujian provinces,and the center of Zhejiang province.Air masses from these potential source regions are transported to Haikou along the trajectories 1,2,and 4.The major contribution regions of O₃ mass concentrations are concentrated in the junction of Hu'nan and Jiangxi provinces and the western part and Guangdong province.The pollutants are transported to Haikou from the inland along the trajectory 2.