Synoptic analyses associated with the aerosol adjoint module of the atmospheric chemical modeling system GRAPES-CUACE are used to investigate characteristics of the atmospheric circulation, the formation and dissipation of air pollutants during a heavy PM_2.5 pollution episode from February 29 to March 6, 2016 in Beijing. The adjoint module is also applied to track the key source areas and sensitive emission period. Analyses reveal that the PM_2.5 concentration in Beijing exhibits remarkable daily variations and reach its peak at 20:00 BJT on March 4, and the observed PM_2.5 concentration attain 506.4μg/m³ at Haidian station. Beijing is controlled by the low pressure during the episode, with less influence of cold air, weak/calm winds, strong inversion of temperature, stable atmospheric stratification, low planetary boundary layer (PBL), facilitating the accumulation of air pollutants. The occurrence of a short-term PM_2.5 decrease is primarily caused by the 500hPa short-wave trough transit and the southerly jet in the PBL. Model results show that the PM_2.5 concentration at the target time of the pollution process in Beijing is affected jointly by the transport from the northeastern and southern regions of Hebei, Tianjin, and parts of Shanxi and Shandong. The peak PM_2.5 concentration at the target time in Beijing responses most quickly to the local emission source and most slowly to the Shanxi emissions. The cumulative contribution of emissions from Beijing, Tianjin, Hebei, and Shanxi to the PM_2.5 concentration in Beijing at the target time during the first 72hours is 31.1%, 11.7%, 52.6%, and 4.7%, respectively. Within 3 hours before the target time, the local emission dominates the PM_2.5 concentration in Beijing, with a contribution of 49.3%, but emissions from Hebei and Shanxi are dominant within 4h to 50h and within 50h to 80h before the target time, with contributions of 48.6% and over 50%, respectively.