To study the size and turnover of the biologically active soil organic carbon pool, which indicate nutrients supplying capacity and cycling in soil, eleven soils collected from Zhejiang Province were used The size of the biologically active soil organic carbon pool C 0 ranged from 184 87 to 3022 41mg/kg and 2 91%～8 94% of total soil organic carbon The turnover rate (k) of biologically active soil organic carbon pool was 0 0070～0 0199d -1 C 0 has significantly positive correlations with total soil organic carbon, total nitrogen, available nitrogen, CEC, K 2Cr 2O 7 readily oxidized organic carbon, soil microbial biomass carbon, soil microbial biomass nitrogen, water soluble organic carbon, hot water extracted organic carbon and light fraction organic carbon,but k has no correlation with all items above (P<0 05) C 0 has no correlation with the percentages of K 2Cr 2O 7 readily oxidized organic carbon, soil microbial biomass carbon, soil microbial biomass nitrogen, hot water extracted organic carbon and light fraction organic carbon to total soil organic carbon However, k has significantly positive correlation with the percentage of water soluble organic carbon to total soil organic carbon (R 2=0 4684, P<0 025) The percentage of water soluble organic carbon to soil total organic carbon was a good indicator to characterize the turnover of biologically active soil organic carbon pool