Based on the observations of SO2 concentrations and meteorological data from a 325-m meteorological tower from 25 Jan. to 2nt Feb. during winter season 2000, characteristics of SO2 pollution in the lower atmospheric layer of Beijing is analyzed. The relation between vertical distributions of SO2 concentration, wind fields and temperatures is studied. Results show that heat island effect is significant in Beijing. Inversions in the near-surface did not occur during observations SO2 was concentrated in the lower layer and distributed homogeneously in vertical when a Lower Level Wind Maximum Core (LLWMC) was formed. SO2 concentrations at three layers increase immediately after breakdown of LLWMC. SO2 was transported upward due to strong thermodynamic mixing during daytime, and a maximum concentration of SO2 appeared to be at 50 m. Heavy SO2 pollution was always an accompaniment of nocturnal calm and surface inversion. Richardson number is always negative at about 120 m, which indicates that the height of the urban turbulent dynamic transport in Beijing is about 120 m in winter. Key words:SO2 ; Vertical distributions; Surface layer; Inversion; Beijing