Abstract: Based on the air quality monitoring data from 2017 to 2019,the HYSPLIT backward trajectory model,cluster analysis,potential source contribution factor analysis（PSCF）and concentration weight trajectory analysis（CWT）were used to analyze the transport paths and major paths correspond to heavily polluted circulation patterns and potential sources of PM_2.5in Yuncheng in autumn and winter.The results show that the easterly wind prevails near the ground corresponding to relatively high pollution frequency,the weak easterly and southwest increase the PM_2.5concentration.Clustering analysis of backward trajectories of PM_2.5in autumn and winter show a great regularity.The trajectories are mainly from the northwest with high frequency of 53.53% but rarely from the east with low frequency of 11.25%.The amount of trajectories from the west and southwest are between them,which are 16.61% and 12.06%,respectively.Different tracks corresponded to different weather patterns,the heavy pollution weather pattern of the northwest and west tracks is mainly as follows:There are mostly“two troughs and one ridge”situation at 500 hPa;Yuncheng is affected by the northwest airflow before the ridge at 700 ～850 hPa;At sea level pressure,the high-pressure front bottom type or uniform-pressure field type is generally observed.The heavy pollution weather pattern in the southwest track is mainly as follows:The 500 hPa is generally straight westerly wind.At 700～850 hPa,Yuncheng is affected by the southwesterly in the east of the trough.The sea level pressure field is the front bottom（bottom）of high pressure or uniform pressure.The potential sources of PM_2.5in Yuncheng are mainly located in southern Shaanxi,eastern Sichuan,southeastern Xinjiang and the southeast part of Gansu.These indicate that the concentration of PM_2.5affecting Yuncheng in autumn and winter is not only from the regional transportation of particulate matter in the southwest part of the Fenwei Plain.Longdistance transportation of particulate matter from Xinjiang and Gansu provinces in the northwest are also the important sources.