Picea asperata is an important afforestation species in the subalpine region of Gansu Province. The estimation of carbon and nitrogen storage in P. asperata plantations is helpful to evaluate the ecological restoration effects after afforestation. To estimate the dynamics and allocation patterns of carbon and nitrogen storage, 16 field plots of different forest ages (including young forests, mid-aged forests, near-mature forests, and mature forests) in the P. asperata plantations in Gannan Tibetan Autonomous Prefecture and Dingxi City were established. Vegetation, litter, and soil were investigated and sampled for laboratory analyses. The results showed that carbon contents of different organs in the tree layer were relatively stable, while nitrogen contents were closely related to organ types. Carbon and nitrogen contents in the same soil layer had no significant difference among different stand ages. The ratio of carbon to nitrogen content was higher in tree layer than that in shrub, grass, and litter layer, and soil layer had the lowest ratio. In this area, the total storage of carbon and nitrogen in the ecosystem was up to 257.75-430.23 and 20.50-29.88 t/hm², respectively. As stand age increased, the biomass carbon storage increased from 15.51 to 143.51 t/hm² while the nitrogen in biomass increased from 0.24 to 1.65 t/hm². However, carbon and nitrogen storage in the soil (0-100 cm) was 242.23-367.79 and 20.26-29.58 t/hm², respectively, and showed no significant differences among stand age groups. Soil stored more than 60% of carbon storage and more than 90% of nitrogen storage in the total ecosystem in each age class. Carbon storage in soil layer, tree layer, and shrub/grass/litter layer accounted for 85.72%, 13.44%, and 0.84% of that in the whole ecosystem, while nitrogen storage in the corresponding layers were 97.60%, 2.08%, and 0.32%, respectively.