Abstract: Soil organic carbon (SOC) sequestration in croplands plays a critical role in enhancing soil fertility,global C cycle and associated climate change.However,soils could potentially sequester additional C following changes in management practices until the maximum soil C capacity,or soil C saturation,is achieved.This paper summarizes the current research advances on SOC stabilization mechanisms,C saturation theory and conceptual models,as well as the methods used to estimate C saturation deficit.Current status of carbon saturation researches of China,and perspectives in future studies are also presented.