Based on conventional meteorological observations from Meteorological Bureau of Jinghong, the air pollutant mass concentration data from Jinghong Environmental Protection Bureau, and reanalysis data of ERA-5 0.25°×0.25° from ECWMF (European Centre for Medium-Range Weather Forecasts) and the Hpsplit backward track model from NOAA(National Oceanic and Atmospheric Administration), the characteristics and causes of a Persistent heavy pollution event in Xishuangbanna region on March 29 to April 5,2020 was analyzed. The results showed that the diurnal variation of AQI(Air Quality Index) and PM2.5 concentration were lower in daytime and higher at night. The cold air is weak and prevailing zonal westerly winds during the pollution period at Low latitude plateau area. Meanwhile，warm advection ahead of a ridge that continuously moves eastwards greatly impacts on the increase of temperature in the middle and lower levels of atmosphere，which is favorable for the formation of the stable atmospheric stratificanon. There is no apparent vapor transfer and no classic wet haze feature. The convection and diffusion has been weakened by Stable temperature stratification and atmospheric circulation. The horizontal and vertical diffusion is reduced by lower mixing layer height and surface ventilation coefficient, which leads to increased concentrations of pollutants. There is positive correlation between the pollutant concentration and the numbers of ignition sources in Southeast Asia from MODIS/Terra satellite monitoring and retrieval. The correlation coefficient of AQI and the number of ignition is as high as 0.5. Furthermore, base on the Hpsplit backward track model, combine with fire point data at that time, the influencing factors of heavy pollution weather in Xishuangbanna from March 29 to April 5,2020 were analyzed. According to the analysis, The pollutants are mainly imported from Maqui Mandalay and East Branch, Myanmar. In addition，xishuangbanna is located in Lancang River Valley. Such a local surrounding terrain blocks the subsequently horizontal transport of air pollutants after accumulcting in xishuangbanna region，which is also a major reason for the occurrence of this pollution event.