Carbon dioxide (CO2) take a large proportion of air. The concentration of CO2 improved from 317 ppm in 1958 to 405 ppm in 2016. It is a global challenge to control and reduce the concentration of CO2. Soil carbon pool is the second major pool of carbon on the earth and has considerable potential to sequestrate CO2. This paper concentrates on the mechanism of soil carbon sequestration including the composition of soil organic matter, existence form, protection mechanism and model of aggregates.

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