The alpine-subalpine area of the eastern Tibetan Plateau, as typical high-altitude low-temperature ecosystem, is one of the most important soil carbon pools in China. The soil there has high content of organic carbon due to abundant biomass of the alpine forest and shrub land distributed in the area, and is considered to be more sensitive to soil warming than that in the tropic or subtropical area. The spatial distribution pattern of soil carbon and its labile fractions with altitude could reflect the combined effects of altitudinal biological and environmental factors, particularly the temperature, on soil carbon dynamics. In this study, total organic carbon and its labile fractions including particulate organic carbon, microbial biomass carbon, light fraction of organic carbon, easily oxidized organic carbon, and water soluble organic carbon in topsoil (0-20 cm) were determined with an aim to understand changes of their characteristics with elvational gradients. The investigated altitude range was from 3200 to 4120 m that was covered by subalpine coniferous forest at 3200, 3340, 3540, 3670 and 3740 m, timberline at 3850 m, alpine tree line at 3940 m, and alpine meadows at 4120 m. The results showed that content of total organic carbon in topsoil increased significantly with altitude in the studied range, indicating that high altitude and low temperature are conducive to carbon sequestration in soil. Content of particulate organic carbon content and its ratio to total organic carbon showed significantly positive correlations with altitude, with its concentration reaching up to 50.81 g/kg and and accounting for 56.52% of total organic carbon, as measured at the highest elevation of 4120 m. Therefore, particulate organic carbon had become the major component of total organic carbon with its ratio gradually increased with altitude. On the other hand, microbial biomass carbon, water-soluble carbon, light fraction of organic carbon, as the group of less affected labile fractions, did not change significantly within the studied altitude range, while the fraction of easily-oxidized organic carbon tended to increase with altitude. To sum up, concentrations of particulate and easily-oxidized organic carbon fractions in topsoil could be used as indicators of labile organic carbon dynamics and balance in subalpine-alpine area at different altitudes. Moreover, soil warming may exacerbate the mineralization of particulate organic carbon, resulting in the decrease of the proportion of total organic carbon in soil. The elevational gradient study offered useful insights into the dynamics of high-altitude soil carbon and the differentiation of its labile fractions. It is indicated that soil carbon pool at high altitude could become a new carbon source under future warming scenarios.