Soil is a core of terrestrial ecosystem, and soil organic carbon is the main part of terrestrial carbon reservior. At present, terrestrial carbon cycle is one of the important components in the research of global change, so it is important to study soil carbon cycle. One precondition of terrestrial ecosystem carbon cycle research is to understand soil carbon dynamics in China. The composition and dynamic change of soil organic carbon is more significant in soil carbon cycle research in China. However, soil organic carbon is not accurately defined in China, so people did not fully recognize its importance to global climate change. This paper adopted the soil distribution area, sampling data and soil organic content from the first soil general survey and applied the technique of GIS to estimate soil carbon reservior in China. Through calculating, the total amount of soil organic carbon is about 1001.8×10⁸t and carbon density is about 10.83 kgC/m² in China. This paper provided basic data and analysis method for global change research and scientific support for policy determination of CO₂ emission in China.