The estimation of regional soil organic carbon pool and carbon sequestration potential is significant in the study of carbon cycle in global climate change. Based on the data from the second national soil survey conducted in 1978-1979 and the project of soil testing and formulated fertilization conducted by Ministry of Agriculture in 2007-2011 and combining with the analysis of survey data and field test data,soil-type method was adopted to estimate the carbon storage and density in farmland soil in Chongqing. By applying GIS technique,the spatial distribution of carbon density of farmland soil in Chongqing was analyzed. Furthermore,fitting analysis was used to reveal the change trend of carbon storage of farmland soil in various districts and counties for the last 30 years,and to estimate the carbon sequestration potential of farmland soil. The results showed that the total storage of organic carbon in topsoil was 233.54*10~6 t,and the average value of soil organic carbon density was 3.08 kg·m~(-2); the organic carbon density of farmland soil was relatively high in southwestern,southeastern and northeastern parts of Chongqing,while it was relatively low in the regions along the Yangtze river mainstream and nearby hilly regions; the carbon sequestration potential of farmland soil in Chongqing was about 30.82 Tg C,and its average value per unit area was 6.71 t·hm~(-2).