Soil is an important organic carbon pool, of which any small change may lead to great variation of CO₂ concentration in the atmosphere. Soil aggregates have the function of physical protection of soil organic carbon. Application of barnyard manure can not only increase the content of soil organic carbon, but also promote formation of soil aggregates, which is of great significance to sequestrating and maintaining soil organic carbon. In this experiment the wet sieving method was used to isolate and fractionate aggregates. It was found after a 8-year stationary field experiment on application rate of manure that application of an appropriate amount of manure significantly increased soil mean weight diameter (MWD), and improved soil structure, but excessive application of manure significantly reduced the content of >2 000 µm aggregates while increased that of 2 000~250 µm aggregates. In Aquic-brown soil, soil organic carbon was mainly distributed in 250~53 µm and 2 000~250 µm fractions of aggregates, accounting for about 73.7%~78.5% of the total soil organic carbon content. With increased input of organic carbon, soil organic carbon was mainly stored in the 2 000~250 µm fraction of aggregates. Manure application significantly sped up renewal of the >2 000 µm fraction of aggregates. The content of light fraction organic carbon in the soil increased with increased manure input, and accounted for 22.1% of the total soil organic carbon in the soil applied with a high rate of manure. The ability of the soil to sequestrate organic carbon is limited, and apparent phenomena of hierarchical saturation are observed. It is, therefore, concluded that in soils deficient in organic matter, it is of great significance to apply organic manure, whereas in soils high in organic matter it is advisable to put in less organic carbon.