Abstract: In November 2015,Beijing-Tianjin-Hebei Region experienced a severe pollution process of wide coverage,long duration,and high intensity. This paper analysed how meteorological conditions work in this persistent severe pollution process by using WRF mesoscale simulation results,in combination with conventional meteorological observation data. The results show that: During the serious pollution process,the mixing layer height fell by about 50%,comparing with the daily mean mixing layer height averaged in the same period of the past 10 years,which greatly compress the pollutant dispersion in vertical space,and the weak low-level wind was not conducive to horizontal diffusion of pollutants; consistently low ventilation index made a large number of pollutants accumulate. Throughout the process,the prevailing wind direction of this area is easterly wind,then southerly wind,and the frequency of southerly wind was the highest in the past 10 years. The special terrain condition,surrounded by mountains on three sides,as well as the development of east airflow pollutants conveyor belt and southwest conveyor belt made a plenty of foreign pollutants transported to the local area; due to the high surface humidity,the visibility decreased and pollutant concentration rapidly rised,leading to much more serious pollution.