Black carbon aerosol (BC) has been measured at IRSA site in Beijing during July and August, 2008. By analyzing these real-time BC data, the concentration distributions and the sources of BC are concluded. The average concentrations of BC in July and Beijing Olympic Games are 4.58 [EQUATION]g/m[EQUATION] and 3.07 [EQUATION]g/m[EQUATION] respectively, that the declining ratio is about 33.0%. It shows that a series of regulations successfully decreased the concentration of BC. The correlation coefficient between daily average concentration of BC and inhalable particles(PM[EQUATION]) is 0.86, while the value of BC/PM[EQUATION] is 1.9%. Through comparing with the BC concentration of summer in 2007, the results indicated that the concentration of BC has reduced during Beijing Olympic Games.