Using the HYbrid Single-Particle Lagrangian Integrated Trajectory(HYSPLIT) model,three cluster analysis of 96 h back trajectories for August 2004 to December 2001 arriving at 15:00 pm in Beijing at three different arrival heights of 10,100 and 500 m have been performed in order to better understand the impact of air transport pathways on urban air pollutant concentrations in cold and warm seasons.Three natural synoptic scale transport patterns were identified with westerly,strong-westerly and slow-easterly from August of 2004 to December of 2007.And five synoptic scale transport patterns were identified during cold seasons and warm seasons.With observational data taken from an urban site of Institute of Atmospheric physics,the impact of each transport pattern on air pollutant concentrations in Beijing were analyzed.The results show high atmospheric pollutant concentrations of both cold and warm seasons always appear in slow-northwestern pathways,the low pollutant concentrations of cold seasons appear in strong-northerly pathways and that of warm seasons appear in both slow-northerly pathways and strong-northwestern pathways.The analytic results indicate low pollutant concentration always appear in long-range transport pattern as the fast wind speed and air pathways from heavy polluted industrial region tend to increase the urban pollutant concentration in Beijing.The bias between the air transport pathway effect and the pollutant concentration distribution in warm seasons indicates that more study are needed on other potential factors effecting urban atmospheric pollutants.