Abstract: The dry adiabatic method was applied to analyze sounding data and normal maximum surface temperatures collected at Beijing observatory during 1984-2013 and calculate daily maximum height of atmospheric boundary layer (MABL) in Beijing area. The mean wind speed and ventilation were obtained simultaneously. Characteristics of the three boundary layer variables and the air pollution index (API) were analyzed to investigate the relationship between the boundary layer variables and air pollution. The results showed that: (1) Monthly mean MABL of about 1600 m is the highest in the spring and early summer (March to June), following by that in the summer and early autumn (July to October), which is about 1300 m; the monthly mean MABL is low in the winter (November, December, and January) with a value of about 1000-1200 m; (2) in the summer, the frequency distribution of the MABL is roughly symmetric with the peak value within the range of 1000-1600 m; in the autumn and winter, the frequency distribution is skewed to the lower side with the largest frequency for the MABL within the range of 600-800 m; the MABL frequency varies greatly in the spring; (3) the mean wind speed in the boundary layer is lowest in the summer; (4) ventilation reaches maximum in the spring, followed by that in the autumn and summer, and it is minimum in the winter; (5) in the autumn and winter, heavy pollution (API>200) is often accompanied with weak winds, low boundary layer height and low ventilation, reflecting the cumulative effect of local pollutants. In the spring, more than half of the pollution events are characterized by high wind speeds and high ventilation, reflecting the dust pollution by external inputs.