Abstract: To investigate the status of background pollution and changes in air quality in the Beijing-Tianjin-Hebei region in the post-Olympic period, automatic environmental monitoring instruments were used to observe concentrations of the main atmospheric pollutants (NO_x, SO₂, O₃ and PM_2.5) at Xinglong regional background observation station during summer for three consecutive years. Transport and sources of air pollutants were analyzed by backward trajectories calculated by the HYSPLIT model. The results showed that the average concentrations of NO_x, SO₂, O₃ and PM_2.5 in this region during the summer were (11.5±5.9), (8.3±7.0), (137.6±38.4) and (50.9±33.0) μg/m³, respectively. The main pollutants at Xinglong station were O₃ and PM_2.5; the number of days in which the daily concentrations of these two pollutants exceeded the secondary standard of China''s ambient air quality standard (GB 3095-2012) (200 μg/m³ for O₃ and 75 μg/m³ for PM_2.5) were 102 days and 60 days, respectively, which accounted for 39% and 23% of the total observation days. These results indicated that atmospheric oxidation and secondary pollution increased yearly. Influenced by the southerly airstream during the summer, air pollutants emitted along the Taihang Mountains and the Shandong Peninsula-Bohai Bay region were transported to Xinglong station, causing major contribution of high O₃ and PM_2.5 pollution in the Beijing-Tianjin-Hebei urban areas and the entire North China area.