A field experiment is carried out to evaluate effects of non-tillage on distribution, content of organic carbon, and microbial carbolic metabolism of soil aggregates in a fluvo-aquic soil under a cropping system of corn-wheat rotation in the Fengqiu National Agro-Ecological Experiment Station, China. The>250 μm fraction of aggregates in the soil was significantly higher (p<0.05) under non-tillage than under conventional tillage, while the 250~50 μm fraction did not vary much between different tillage methods, and the contents of organic carbon in these two fractions were higher under no-tillage.The 50~2 μm fraction was significantly lower (p<0.05) under no-tillage than under conventional tillage, while the<2 μm fraction showed no much difference between tillage methods, and the organic carbon in these two fractions did not either.The increase in the 250~50 μm fraction and the resultant decrease in the 50~2 μm fraction made the former ranking first in contribution to the total organic carbon in the soil.BIOLOG analysis indicates that the two treatments, non-tillage and conventional tillage, differed significantly in carbolic metabolism of soil microbial communities in various particle size fractions, with the former being obviously lower than the latter in the 250~50 μm and<2 μm fractions.All demonstrate that non-tillage favors congregation of small particles into macroaggregates and increases the content of organic carbon in the>50 μm fraction, while microbial carbolic metabolism in the 250~50 μm fraction weakens thus leading to higher stability of organic carbon in the soil.