In order to reveal the meteorological reasons for the formation and development of regional atmospheric pollution,according to the large-scale weather background,NCEP reanalysis data and surface atmospheric composition observation data were used to divide the persistent air pollution processes over central Liaoning Province during 2010-2012 into five types,namely,Mongolia High Type,Denatured High Type,Mongolian Cyclone Type,Weak Depression Type and Jiang-huai Cyclone Type.Further physical characteristic study shows that the pollution events caused by Mongolian Cyclone account for the highest ratio of 32.7% whereas those caused by Jiang-huai Cyclone account for the lowest ratio of 6.1%.All the eleven events caused by Mongolia High appear in winter while all the four events caused by Weak Depression appear in summer.The fifteen events caused by Denatured High appear in winter,autumn and spring,whereas the three events caused by Jiang-huai Cyclone appear in summer,autumn and winter.The sixteen events caused by Mongolian Cyclone appear in all the seasons.All the above show that autumn and winter are the high-occurrence seasons for Mongolia High Type,Denatured High Type and Mongolian Cyclone Type,and summer is the high-occurrence season for Weak Depression Type and Mongolian Cyclone Type.Boundary layer physical mechanism study shows that the horizontal convergence,vertical transport and atmospheric stratification stability of Jiang-huai Cyclone Type and Mongolia High Type are similar,whereas the inversion of the former is stronger.As for Jiang-huai Cyclone Type,the relative humidity is as high as over 95% and the downward flow is as strong as 0.2-0.4 Pa/s,along with the inversion strength at 0.7℃/hm and inversion height at 925 hPa.Compared with these two types,the horizontal convergence of the other three is similar,but the downwind,atmospheric stratification stability and inversion are significantly weaker,even rarely appear.