Black Carbon (BC) concentration at the urban site was measured using Multi-Angle Absorption Photometer (MAAP, Model-5012) around 2008 Beijing Olympic Games, and its temporal variation pattern and controlling factors were investigated according to corresponding meteorological data and traffic controlling policy during and after the Olympic Games period. Frequency analysis indicates that BC concentration for peak frequency before implement of vehicles control policy (before 20 Jul) was 3.4 μg·m-3, and it enhanced to 3.9 μg·m-3 averagely during 20 Jul to 7 Aug. During the Olympic Games period, BC concentration declined to 2.5 μg·m-3, 31% lower than the value before the Olympic Games period. According to meteorological data, the increase of rainfall amount and frequency of northerly wind (from 24.1% to 38.8%) might play an important role in the decrease of BC concentration in Beijing urban area. Motor vehicles monitoring data at Jianxiang Bridge of the Badaling Expressway show that the traffic mount has declined by about 30% during the rushing hours of weekday, which might be another possible contribution to the decrease of BC concentration.