Abstract: Based on the organic carbon data obtained from the 1:250 000 land quality geochemical survey, the soil carbon storage is calculated with unit soil carbon amount method. The results show that the organic carbon storage in Xunke Plain is 87.43 Mt in the surface soil (0-0.2 m), 332.70 Mt in the middle soil (0-1.0 m), and 457.62 Mt in the deep soil (0-1.8 m), with the organic carbon density of 6.52, 24.82 and 34.14 kg/m², respectively. The soil organic carbon storage and density are calculated in terms of landform, soil, land use and ecosystem types. Compared with the second national soil survey results in 1986, the soil organic carbon change in Xunke Plain shows a carbon source effect, with the soil organic carbon in the whole region decreased by 8.48 Mt and organic carbon density decreased by 8.94%.