Abstract: Properties of urban forest soils have been greatly altered by human activities during the progress of urbanization. The urbanization changed not only the scale of soil carbon pool, but also the composition and characteristics of organic carbon in urban forest soil. Total soil organic carbon(SOC), dissolved organic carbon(DOC), microbial biomass carbon(MBC), readily oxidation carbon(ROC)and light fraction organic carbon(LFOC)in 0-30 cm forest soil layers under seven different function areas in Nanjing were studied. The distribution of urban forest soil organic carbon and correlations between different fractions of soil organic carbon were analyzed. The results showed that all of the organic carbon fractions enriched in 0-10 cm soil layers apparently. The soil active organic carbon content in different functional areas decreased with soil depth increasing. Human disturbance exerted great influence on the content of soil organic carbon. The natural forest soil in the suburb accumulated more ROC and MBC. Due to traffic related organic matter input, urban road green belt soils had higher content of SOC, DOC and LFOC. Soils in park, campus and residence community with frequent human activities had lower level of active organic carbon content. There was a significant correlation between soil total organic carbon and the active organic carbon.