The carbon (C) cycle in alpine ecosystems is sensitive to climate change, but information about the C storage in its undergrowth is scarce. In October 2017, a total of 6231 Pinus pumila (Pall.) Regel trees were investigated for above-ground growth and density in 60 sub-plots (10×10 m) from 12 stands (50 × 50 m) along the altitudinal gradient (800-1500 m a.s.l.) in Great Khingan Mountains, Inner Mongolia, Northeast China. Sites were characterized by different crown densities (CDs) from 20% to 90%. Height and root-collar diameter (RCD) were higher in stands with CDs of 40-70% than CDs of 20-30%. Stem density (SD) and crown area (CA) had a positive correlation with altitude and CD. Equations from local shrub models were used to adapt the allometric growth models for estimation. There were variations in estimated above-ground C density depending on the model and the involvement of the canopy area. Above-ground C storage in P. pumila individuals ranged from 0.05-2.46 kg tree-1, which corresponds to C storage density ranged from 0.17-37-ton ha-1. The C density in P. pumila increased with crown density instead of stem density along increasing altitudinal gradients and increasing RCD. Hence, the crown density and diameter of a P. pumila plant can be used to predict the above-ground C density of its natural population.