Abstract Recent spatiotemporal soil organic carbon (SOC) changes in croplands of China were estimated by using a modified and validated Agro-C model. Estimates revealed that SOC in approximately 81% of China's croplands increased from 1980 to 2009. SOC increases in east, central, south, and southwest China were more significant than those in other regions of the country, while a decrease in SOC was pronounced in Heilongjiang Province in northeast China. Overall, we estimated that China's croplands covering an area of 130million hectare sequestered 730 (329 to 1095) Tg C in the topsoil to 30cm depth, during this period. Approximately 73% of the SOC sequestration occurred in east, central and south China. The carbon sequestration was attributed to the improvement of crop production and the decrease in the removal of crop residues. Soils rich in organic carbon that received relatively low carbon inputs during the same period, however, suffered net carbon losses in Heilongjiang Province.