Abstract: This paper investigated the characteristics and sources of organic carbon(OC) and elemental carbon(EC) in PM_2.5 during the heating season in Beijing. PM_2.5 samples were collected at the Beijing Normal University sample site during the period of December 2011 to February 2012. This study also analyzed the concentrations characteristics of PM_2.5,OC and EC,calculated the concentrations of the secondary organic carbon(SOC) based on the minimum ρ(OC)/ρ(EC) ratio method. Besides,the sources and source contributions of OC and EC were analyzed qualitatively and quantitatively.Resultsshowed that the average concentration of PM_2.5 was(90.69 ±61.86) μg/m³,the average concentration of OC and EC were(21.91 ±12.02),(5.03 ±2.58) μg/m³,accounting for 24.16% and 5.55% of PM_2.5,respectively. The average concentration of SOC was(8.37 ±6.05) μg/m³,accounting for 37.27% of the total organic carbon(TOC). The high correlation coefficient of OC and EC showed that the source for OC and EC was the same,mainly from the vehicle emission,the coal combustion. The vehicle emission was the major source,with a contribution of 44.70% to the OC and EC. As a consequence,controlling the number and reducing the emissions of motor vehicles have become an important measure to improve the atmospheric environment quality in urban areas.