Abstract:Soil organic carbon (SOC) is an important asset of ecosystems and plays a key role in the global carbon balance. Since the 2015 Paris Climate Conference, promoting SOC accumulation in terrestrial ecosystems has received special attention and is considered to be the most important land-based action of mitigating the rising atmospheric CO2 concentration. Starting from serving this goal, this paper reviews and summarizes the history of the global exploration of SOC formation mechanisms over the recent decades. Including the global distribution law of SOC, the SOC cycle processes and the corresponding physical, chemical and biological mechanisms at scales that are smaller than plot, and the mechanisms of soil carbon sequestration at scales that are larger than plot. Finally, an example of the SOC accumulation mechanisms of mature forest is given. So, the exploration process of the SOC formation mechanisms is actually the process of seeking theoretical guidance for promoting soil carbon sequestration.