In order to accurately estimate the size of carbon pool in the forest region of Xiaolong Mountains (Gansu Province, China), carbon content rates (CCRs) of dominant forest vegetations (13 tree species, 14 shrub species, 10 herbaceous plants) and the forest litters of 7 stand types were measured with dry combustion method. Based on the biomass data from sample plots, the average CCR of tree layer, carbon storage density and carbon storage of forest vegetation were calculated, as well as the carbon storage allocation of each component in 8 forest stands. The average CCR of the 13 tree species, Quercus Aliena var. Acuteserrata, Pinus tabulaeformis, Quercus variabilis, Betula platyphylla, Betula albo-sinensis, Larix kaempferi, Pinus armandii, Picea asperata, Abies chensiensis, Fraxinus mandschurica, Cornus macrophylla, Acer mono, and Quercus liaotungensis ranges from 0.4501 to 0.5049. The mean CCR of shrubs (14), herbaceous plants (10) and forest litters (7 stands) are 0.4446, 0.3270 and 0.4221, respectively. In this region, the average CCR of tree layer in the 8 stands varies between 0.4676 and 0.4976. Results show that the carbon storage density of forest vegetation in Xiaolong Mountains is 39.4254 t hm^-2, and carbon storage is 13.3579 Tg. In the tested 8 stands, carbon storage allocations of tree layer, shrub layer, herb layer and forest litters are 98.07%±0.73%, 1.38%±0.43%, 0.17%±0.08% and 0.37%±0.37%, respectively. We conclude that the estimated tree layer carbon storage density in Xiaolong Mountains is similar to the reported value in other areas of China and around the world.