<p>Purpose: To research the influence of different densities of Platycladus orientalis plantation on the allocation characteristics of carbon storage in the ecosystem, the density regulation experiment on the Pinus massoniana plantation with different densities was carried out to discuss the change of the carbon storage of the ecosystem. Method: The density regulation experiment was carried out using random block design along contour line. Through the estimation of tree layer biomass of single Pinus massoniana, the determination of the carbon storage in the tree layer of Pinus massoniana, the estimation of the understory shrub, the grass layer, and the wood layer, the determination of carbon storage in vegetation and litter layer under forest, the determination of organic carbon content and carbon storage in the sample, and the carbon storage of the plantation ecosystem of different stand density sample plots, the effects of stand density on biomass and carbon storage of Pinus massoniana plantation were analyzed. Results: The results of average carbon storage per unit area of Pinus massoniana plantation was different stand densities are 94.11 t/tm2 (1679 plants t/hm2), 79.06 t/tm2 (2250 plants / hm2), 73.32 t/tm2 (2800 plants / hm2). With the increase of stand density, the proportion of carbon storage in Pinus massoniana plantation decreased. This is because the larger the stand density, the more trees with small and medium diameter are grown in the Pinus massoniana plantation. The average diameter at breast height of the stand is very small, and the biomass of single tree decreases. The density is most beneficial to the improvement of the carbon storage of the tree layer. Conclusions: Density regulation promotes the accumulation of carbon storage of the Pinus massoniana plantation and increases the carbon storage of understory vegetation, litter, and soil layer.</p>