This study applied the CAMx model to study the regional transport of various PM2.5 components in Beijing during a severe pollution episodes. The results revealed that during the episodes, Beijing had the average PM2.5 pollution value of 119 µg m–3. It was 1.58 times of the PM2.5 national air quality standard (75 µg m–3 Level II). The wind speed was low (< 2 m s–1) and relative humidity reached 98%. The anticyclone in Eastern China showed weak local flow fields and southerly winds at the surface and strong temperature inversion under 1000 m, which promote pollution accumulation. The contribution of monthly regional transport to primary PM2.5 components and SO42–, NO3–, and secondary organic aerosol concentrations in Beijing were 29.6%, 41.5%, 58.7%, and 60.6%, respectively. The emissions from Baoding had the greatest effect on the primary components of PM2.5 (6.1%) in Beijing. The emissions from Tianjin had the greatest influence on the secondary components of PM2.5 concentrations. These values indicated that the secondary components of Beijing’s PM2.5 are more easily affected by transboundary transport than are the primary components. The present findings suggest that control strategies for PM2.5 pollution should include coordinated efforts aimed at reducing secondary aerosol precursors (SO2, NOx, and VOCs) from long-range transport and local generation in addition to primary particulate emissions.