The active C pool and CPMI(C pool management index) of soils under different agricultural ecosystem were discussed using potassium permanganate oxidation in this paper.Results indicated CPMIs were significantly affected by fertilization,climate,soil utilization style and cultivated age et al.The active C varied from 0 49 to 4 99mg/g, and CPMI from 51 6 to 165 in the experimental soils. The order of CPMI in red soil of tropical zone influenced by different fertilization treatments was GM(green manure)>FYM (farmyard manure)>FYM+NPK>REF(reference)>NPK>CK.In subtropical zone,the corresponding order was RSC(rice straw compost)>FYM>FYM + NPK>REF>CK in paddy soil,while in yellow brown soil,compared with reference,CPMI of GM,FYM,FYM+NPK incremented by 50%,45 9% and 21 9% respectively.That of NPK and CK decreased by 6% and 38 1%.In meadow soil of temperate zone,compared with CPMI influenced by 5 year fertilization,CPMI for 10 year FYM application incremented by 28 4%,for FYM+NPK by 19 7%,while for NPK and CK decreased by 8 7% and 17 8%.Correlation analysis indicated CPMI was not only related or extremely related to total N,total P,hydrolyzable N,readily available P,K and pH,but also sensitive to agricultural practices.This showed it is practical using CPMI to reflect the impacts of agricultural measures on soil fertility and the dynamics of C pool variation.