The characteristics of the pollution process occurred in Beijing, Tianjin and Hebe province during 16~21 December 2016, the relationship between the pollution process and meteorological conditions were studied by using the data of routine ground observation, Micropulse Lidar (MINI-MPL), wind profiler radar, and atmospheric composition of the Ministry of Ecology, etc. of China Meteorological Administration. The static state of the atmosphere, the prevailing southerly airflow in the lower atmosphere, the continuous increase of atmospheric humidity, and the special terrain surrounding the mountains on three sides of Beijing which was not conducive to the diffusion of pollutants were the important factors causing the serious air pollution in Beijing. During the period of heavy pollution, the pollutants mainly accumulated below 800 meters. When the pollution was serious, the height of pollutants was only about 400 meters. Wind profiler radar retrieved wind field showed that the low level of PM_2.5 concentration rose rapidly during two periods, accompanied by persistent southerly or easterly winds. During the pollution process, the inversion structure was obvious, and the rapid development of two pollution stages occured in the two periods of the strongest inversion. In this polluted weather process, the depolarization ratio of lidar was less than 0.25, reflecting that the pollution was mainly caused by human activities. In the early stage, primary particulate matter was the main pollutant, and in the later stage, secondary transformed particulate matter was the main. The depolarization ratio showed obvious daily change in the early stage of pollution process, and the depolarization ratio was higher in daytime than at night.