Abstract: Study on regional characteristics of soil organic carbon (SOC) in the main region of cultured tobacco in Yunnan, the tobacco-growing soil profiles were collected. According to the content of soil organic carbon density, vertical distribution characters, and the relationships between the soils organic carbon and the soil physical and chemical properties were analyzed. The results showed that: (1) the content of tobacco-growing soil organic carbon density was 10.21 kg/m2. There were high content of soil organic carbon density in red soil, and low content of soil organic carbon density in purple soil and yellow soil. (2)The content of soil organic carbon density showed a reduction in a deeper soil stratum. There was great difference in yellow soil organic carbon density with variation coefficient of 122.35%. Red soil showed that the carbon density was stable and the coefficient of variation was 17.67%-49.60%. (3)The tobacco-growing soil organic carbon density showed a positive correlation with soil water retention and soil clay content, showing no significant correlation with soil porosity. The ratio of organic carbon to nitrogen (C/N) ranged from 1.58 to 14.00. The ratio of organic carbon to phosphorus (C/P) ranged from 1.26 to 34.08. Red soil had the highest ratio of C/N and C/P.