The monitoring results of atmospheric pollutants, surface observations of meteorological elements, and ERA5 reanalysis data from European Centre for Medium-Range Weather Forecasts (ECMWF) are used to analyze the variations of atmospheric pollutants and meteorological elements during a typical severe air pollution event in Qingdao from 17 to 22 December 2016. The observational analysis indicates that the pollution event persists for more than 5 d, within which the period from 19 to 22 December is classified as severe pollution with daily average PM2.5 mass concentration higher than 150 μg·m-3. The pollution event can be divided into three stages according to the variations of meteorological conditions and PM2.5 mass concentration. 1) During the accumulating stage (from 02:00 BST on 17 to 08:00 BST on 19) of pollutants in Qingdao, the research area is controlled by southwesterly winds, resulting in a gradual increase of PM2.5 mass concentration. The maintenance of the trough at 700 hPa and the persistence of the southerly and southwesterly winds in front of the trough are unfavorable to the downwind diffusion and dilution of pollutants, and the increase of relative humidity near surface at the same time is an important factor for the formation of the severe air pollution. 2) The maintaining and intensifying stage (from 09:00 BST on 19 to 20:00 BST on 20) of the pollution event in Qingdao is accompanied with high relative humidity and very weak surface wind, which are unfavorable to the diffusion of pollutants, and PM2.5 mass concentration is the highest. 3) During the dissipating stage (from 21:00 BST on 20 to 08:00 BST on 22) of pollutants in Qingdao, the PM2.5 mass concentration gradually decreases, accompanied with the increase of wind speed from the middle and lower troposphere to surface and the weak precipitation, which are favorable to the diffusion of pollutants and wet scavenging. The WRF-Chem model can simulate the variations of meteorological elements and PM2.5 mass concentration in Qingdao. The simulation shows that the pollutants within Shandong Province contribute to 49.5% of PM2.5 mass concentration in Qingdao, and the interprovincial transport of pollutants also contributes significantly to this pollution event, e.g. the pollutants from Anhui and Jiangsu provinces (to the south of the research area) contributing up to 25.5% of PM2.5 mass concentration in Qingdao.