By using the USCA (Unit Soil Carbon Amount) method, soil carbon storage in Northeast Plain of 230 000 km2 was calculated based on the multi-purpose regional geochemical survey. The results show that topsoil (0~20 cm) organic carbon storage is 768.07 Mt with carbon density of 3 327.8 t/km2, subsoil (0~100 cm) organic carbon storage is 2978.41 Mt with carbon density of 12 904.7 t/km2, and deep soil (0~180 cm) organic carbon storage is 3 729.16 Mt with carbon density of 16 157.5 t/km2, which stay on the national average level. This research will provide basic knowledge to understand soil carbon distribution and to study the potential for soil carbon sequestration.