Abstract: From March 2007 to May 2008, 56 weekly PM2.5(suspended particulate matter with aerodynamic diameter less than 2.5μm) were collected at the east crossing of Chengfu Road, Beijing, China. The concentrations of 15 elements in PM2.5 samples were measured by HR-ICP-MS. Factor analysis(FA) was performed in order to characterize the chemical properties and the origin of PM2.5. The total mass of 40 intensive daily (24h) PM2.5 samples were measured during the Olympic Games and the Paralympics Games, in order to investigate the pollution level when traffic control was carried out. The results show that the average mass concentration of PM2.5 was 72.9 μg/m3, which was around 5 times higher than that of the limiting value of 15 μg/m3 (established by U.S. Environment Protection Agency) from spring 2007 to spring 2008. During the Olympic Games, the average mass concentration of PM2.5 was 40.7 μg/m3. The statistical evaluation of the data identifies three main sources responsible for PM2.5 in Beijing: ①A combination of road traffic, industry emissions and coal combustion, characterized by Cu，Zn，As，Sn，Sb，Cd and Pb； ②Soil dust, construction sites and fine dust particles; ③Re-suspension and/or mobilization of geogenic soil particles, accounting for 41.2%, 31.4% and 12.2%, respectively of the total variance.