Properties of soils in urban forests have been greatly altered by human activities during the process of urbanization. The distribution of black carbon in urban forest soils shows large variation resulting from its diverse origins and as a result of human activities. The concentrations and the potential origins of black carbon in urban forest soils from different functional areas were studied. Concentrations of black carbon in urban forest soils in different functional areas varied significantly, from 0.77 g/kg to 21.27 g/kg. The concentrations of black carbon in road side green belts soils were significantly higher than those in soils of other functional areas. Residential areas had the lowest concentrations of soil black carbon. The concentrations of black carbon in surface soil (0-10 cm) were higher than those in subsurface soil (10-30cm) and black carbon was enriched in surface soil. The ratio of black carbon to organic carbon (BC/SOC) in road green belt surface soils was 0.55. In roadside green belts areas, the carbon isotope ratio of soil black carbon (δ¹³C_PDB) was -27.04‰, which is significantly different than that of other functional areas. These results indicate that the accumulation of black carbon in urban forest soils is strongly influenced by traffic pollution.