Abstract: Black carbon (BC) is an important component in aerosol. At present, BC has exceeded CH₄, and become the second most important factor influencing the global warming, next to CO₂. In this work, the time series characteristics and influence factors of BC in aerosol in Fangshan District of Beijing were studied based on the BC concentrations in fine particle (PM2.5) air filter samples measured by reflection method using an Aethalometer and relevant meteorological data collected during the period of May 2007 to Oct. 2009. PIXE was used to determine multielements in PM2.5 aerosol samples. The strong positive correlation between BC and S implies both are mainly from man-made pollution, while the very weak correlation between BC and dust-carrying Si indicates they are from different sources. The results from this work were compared with those of other cities and countries reported in literatures. Potential source directions of BC were also studied via the conditional probability function (CPF) and the Wind Rose software.