This study was conducted to determine forest carbon content, density, and the characteristics of carbon distribution in the Evergreen Broad-leaved and Deciduous Broad-leaved mixed forest in Lei Gongshan Nature Reserve, Guizhou, China. Results indicated carbon content in the ecosystem varied significantly (P < 0.01) between trees, shrubs, herbs, litter and soil: 418.58 g/kg, 387.26 g/kg, 382.80 g/kg, 378.11 g/kg, and 31.48 g/kg, respectively. Among the various organs of a tree, the carbon content was distributed as follows: trunks > roots > leaves > branches. For shrubs, the carbon content was distributed as: stems > leaves > roots. For herbs, the above ground carbon content was higher than the below ground carbon content, while for all of them, the differences in carbon content among the different organs of a tree, shrub or herb was insignificant (P > 0.05). The average carbon content of all vegetation was 40.02%, when all types (trees, shrubs, and herbs) and all plant organs were considered. The carbon content in the litter of the un-decomposed layer was higher than in the semi-decomposed layer, though the difference was not significant (P > 0.05). The soil carbon content was highest in the soil at a depth of 0 to 20 cm and soil carbon content generally decreased inversely and significantly with soil depth (P < 0.01). The most of the carbon in the entire ecosystem (234.68 t/hm²) was divided between the soil (170.00 t/hm²) and trees (57.02 t/hm²) with the remainder being tied up in the litter (5.48 t/hm²), shrubs (1.81 t/hm²) and herbs (0.37 t/hm²), and accounting for 72.44%, 24.30%, 2.34%, 0.77% and 0.16% of the soil carbon of the entire ecosystem, respectively. The carbon density in the vegetation was 58.79 t/hm² accounting for 25.09% of that in the entire ecosystem. The carbon density among the various organs of a tree could be classified as: tree trunks > roots > branches > leaves and among them the carbon density of the tree trunk was the highest, accounting for 52.43% of the total. This indicated that tree trunks, among all the organs of a tree, were the major contributor not only to the tree's capacity to accumulate carbon but also determined the quantity of carbon an ecosystem could store. The aboveground carbon density was 2.85 times higher than the underground density for shrubs and the aboveground carbon density was 1.64 times higher than the underground carbon density for the herbs. The carbon density in the soil ranged from 27.40 t/hm² to 70.40 t/hm² and it decreased with an increase in the soil depth. The carbon density in the topsoil (0 to 20 cm deep) was 70.40 t/hm² and was prominently higher than that of any other soil depth (P<0.001), and the carbon density in the topsoil contributed 41.41% of the entire soil carbon mass measured at depths of 0 to 80 cm, which indicated that carbon accumulated significantly near the topsoil. Therefore, the control of soil and water erosion could effectively maintain the soil's capacity to sequestrate and fix soil organic carbon.