Abstract: The natural secondary forests of Betula luminifera in west Guizhou were taken as the subject to study the carbon content, carbon density and the distribution characteristics of carbon based on an integrated approach of field investigation and lab analysis. The results indicated that the carbon content in the ecosystem of the Betula luminifera forests in descending order was trees(495.27 g/kg), shrubs(487.10 g/kg), herbs(456.57 g/kg), litter(431.57 g/kg)and 0-80 cm deep soil(36.31 g/kg)with significant difference between them. The average carbon content in the vegetation was 483.55 g/kg. The carbon content in the different organs of the trees in descending order was trunk, branches, foliage and roots, and the carbon content for both the trunk and the branches increased with the increase in the diameter at breast height(DBH). The carbon content above ground was higher than that underground both in the shrubs and herbs. The carbon content in the soil decreased with the increase of the soil depth. The carbon density of the ecosystem in average was 224.67 t/hm² and in descending order was the 0-80 cm deep soil(201.3 t/hm²), the trees(17.22 t/hm²), shrubs(3.14 t/hm²), litter(2.49 t/hm²)and herbs(0.82 t/hm²), and these respectively contributed 89.60%, 7.53%, 1.40%, 1.11% and 0.36% of the entire ecosystem. The carbon density in the vegetation was 21.18 t/hm², accounting for only 9.29% of the ecosystem. The carbon density in the surface layer(0-20 cm deep)of the soil was 76.7 t/hm², contributing 38.08% of the total soil mass(0-80 cm deep), significantly higher than that in any other soil layer, which indicated that carbon was significantly concentrating on the surface layer of the soil. The net carbon sequestration in the natural secondary forests of B. luminifera was 3.58 t/(hm²·a), which was equal to 13.12 t/(hm²·a)CO₂, and it proved that the natural secondary forests of B. luminifera was an important sink of atmospheric carbon, and it was quite meaningful to maintain and well manage the present natural secondary forests of B. luminifera.