The dynamics of soil organic carbon (SOC) plays an important role in the global C cycle,while decomposition rate of SOC is essential to understanding of soil C dynamics.The objective of this study was to explore how the natural ¹³C abundance method can be used to determine decomposition rates of organic carbon in whole soil and heavy faction of red soils using a laboratory incubation experiment.The soil samples used in the test were collected in March 2003 from a longterm field experiment at Yingtan State Key Agro-Ecological Experimental Stations in China and incubated aerobically at 30℃ in the dark for 180 days.Organic C contents and stable C isotope ratios of the whole soil and its heavy fraction were determined with an elemental analyzer and an isotope ratio mass spectrometer.Results show that the decomposition rates of native organic carbon in the whole soil ranged from 8.2×10^-4d^-1 to 22.0×10^-4d^-1,and in the heavy fraction from 4.0×10^-4d^-1 to 15.6×10^-4d^-1 for red soil incorporated with maize stalks.They were faster in soils incorporated with maize stalks than in soils without maize stalks,which suggests maize stalk incorporation may obviously stimulate the turnover of native organic carbon.Moreover,they were faster when the maize stalk application rate was 10% than when it was 5%,indicating that decomposition rate was related to amount of fresh organic carbon supplied by maize stalks incorporated into the soil.The findings will serve as a foundation for further studies to investigate turnover of SOC fractions using the natural ¹³C abundance method.