The natural abundance of stable carbon isotopes (δ¹³C) can reveal the dynamic changes of organic carbon over time and illustrate the characteristics of functional changes in ecosystems. Using 14 dominant tree species in the secondary forest in northwestern Guizhou, the organic carbon contents and δ¹³C values in leaves, litter, and root-zone soil were measured to analyze the correlation between carbon content and δ¹³C abundance at different levels. The results showed that:the carbon content of leaves of the 14 dominant tree species was 404.67-487.14 g/kg. Generally, the carbon content was higher in conifers and lower in evergreen shrubs. The δ¹³C value was -31.2‰ to -27.1‰, and the change with life form was not obvious. The litter carbon content was 414.62-561.31 g/kg, which was consistent with the change of leaf carbon content; the δ¹³C value was -31.5‰ to -27.3‰, and the changing characteristics of life form in tree species were not obvious. The carbon content in root-zone soil was 10.02-91.59 g/kg, the δ¹³C value was from -26.8‰ to -22.5‰. The carbon content was higher in deciduous trees, such as Rhododendron simsii and Populus alba. There was no significant correlation between the carbon content of leaves, litter, and root-zone soil at different levels and the abundance of δ¹³C value. A positive correlation was found between the abundance of δ¹³C value and carbon content at different levels. The results could help to reveal fundamental information of the carbon cycle process in forest ecosystems and provide a theoretical basis for forest vegetation restoration.