Abstract: Effects of vegetation and fertilization on black soil labile organic carbon and carbon management index(I_CM) were studied in a long-term fertilization experiment.Soil labile organic carbon was measured with KMnO₄ oxidation method,using three concentration levels,33,167 and 333 mmol·L^-1 into three fractions,namely,high labile organic carbon,moderate labile organic carbon,and low labile organic carbon.Results indicate that vegetation and fertilization management showed remarkable influence on formation of labile organic carbon pool of black soil.In the simulated natural ecosystem,22 years of cultivation increased organic carbon content by 13.2%,labile organic carbon content by 39.9%,and carbon management index(I_CM) by 51.4 in the 0-20 cm soil layer of Treatment GF(grassland),while in the farmland ecosystem,15 years of cultivation with application of chemical fertilizers and organic matter did increase organic carbon content by 25.48%,labile organic carbon content by 30.71%,and I_CM by 33.0 in the 0-20 cm soil layer.The correlation coefficients of I_CM were 0.982,0.955 and 0.652,with labile organic carbon,high labile organic carbon,and moderate labile organic carbon.Moreover,total organic carbon,and nitrogen were found to have significant correlation with the three kinds of labile organic carbon.