Abstract: The spatial structures of atmospheric pollution during two advection fog processes were observed in Beijing in February 2007 using laser radar and an atmospheric pollution monitoring web. The processes were studied by analyzing the vertical structure of light extinction properties of atmospheric aerosol in the course of fog formation and dispersion and analyzing the horizontal distribution andevolution of the concentration of surface atmospheric pollutants. The results were as follows: air diffusive conditions worsened and the accumulation effect ofair pollutants became obvious before fog formation. However, the increase of humidity could accelerate the wet deposition rate after the formation of fog, which lessened air pollution. The difference of thermodynamic and dynamical character before and after fog formation can strongly influence pollution vertical distribution, but not the horizontal distribution, which was subject to the transportation convergence around Beijing. Humidity played an important role in atmospheric pollution on the foggy days.Wet depositions (fog scavenging) of SO₂ and NO₂ were 48.0 and 30.8 g/km², respectively, which were reduced by 56% and47% during the February 21-22 fog event, and 16.3 and 14.3 g/km², respectively, during the February 25-27 fog event.