Abstract: Based on the monitoring data of ambient air quality, weather observation data, and the data of energy consumption and main atmospheric pollutants emission, the evolution of main pollutants emission and energy structure in China since 2000 was analyzed. The spatial distribution of allowable emission of main pollutants of enterprises which applied for emission permits in China was discussed, and the two serious pollution processes occurred in Beijing, Tianjin, Hebei and surrounding areas from late-January to mid-February 2020 were studied and revealed. The results showed that among the enterprises that had obtained emission permits, 73% of VOCs emission enterprises, 62% of NO_x emission enterprises and 48% of particulate matter emission enterprises were concentrated in Beijing-Tianjin-Hebei region and its surrounding areas. The dense emission sources provided sufficient pollutants and precursors for heavy pollution. Meteorological conditions played an important role in the two typical heavy pollution events. The first heavy pollution case (January 25-28) was dominated by high pressure, which restrained the horizontal diffusion of pollutants, while there was inversion in the lower atmosphere, which restrained the vertical diffusion of pollutants. The second heavy pollution case (February 9-13) was located in front of low pressure, which restrained the diffusion of pollutants due to the weak low pressure and strong inversion on the ground. The impact of setting off fireworks on PM_2.5 concentration was basically only 5 to 10 hours, and this impact on the two pollution process was limited. At present, there is a long way to go to improve the ambient air quality in Beijing-Tianjin-Hebei region and the surrounding areas. For the improvement of the air quality, it is vital to put forward scientific and reasonable air pollution prevention and control policies, research and develop appropriate pollution prevention and control technologies, take practical and sustainable measures and actions, and improve relevant standard systems.