Decomposition rates of organic carbon fractions and their responses to exogenous carbon are important for forest carbon modeling.In this study, a laboratory incubation experiment was conducted to investigate the distribution of exogenous carbon(~(13)C-glucose) in soil fractions and the decomposition rates of organic carbon fractions using ~(13)C stable isotope technique.Soil collected from Chinese fir plantation,which was incubated at 15 ℃ or 25 ℃ for 112 days. The results showed that the ~(13)C remaining in bulk soil,light fraction and heavy fraction (as % of ~(13)C addition) decreased with incubation time,about 18.9% ~22.0% of ~(13)C-labeled still remained in bulk soil after 112 days.The decomposition rates of SOC and HFOC and LFOC were estimated using first-order decay equation.The decomposition rate accounted for 4.4*10~(-4)~9.7*10~(-4) d~(-1) for SOC, 3.4*10~(-4)~7.0*10~(-4) d~(-1) for HFOC and 1.1*10~(-3)~4.6*10~(-3) d~(-1) for LFOC.Exogenous carbon significantly affected the decomposition rates of organic carbon fractions.Temperature increase stimulated the decomposition of LFOC,but suppressed the decomposition HFOC under exogenous carbon addition treatment.Therefore,the LFOC may be more sensitive to global warming than the HFOC in tested soil.