Abstract: Based on the biomass investigation data of Pinus sylvestris var. mongolica plantation with different ages, the compatible tree biomass models of P. sylvestris var. mongolica plantation biomass of different ages were established in this paper and the changes of carbon density and storage of tree layer, undergrowth layer and died ground cover in the forest were discussed. The results showed that the carbon density of different organs varied in the following order: leafbranchstemroot. The arithmetic average carbon density of different organs increased with forest age, which were 449.5, 460.2, 470.8, 485.1, 489.2 and 513.6 g/kg for the plantations of 27, 30, 32, 36, 40 and 44 years old. There was no obvious trend in understorey of plants and died ground cover. The total carbon storage of P. sylvestris var. mongolica forest increased with forest age, ranging from 37.14 t/hm2 in 27 years old forest to 168.46 t/hm2in 44 years old one. The order of carbon storage of different layers in the forest was treedied ground coverundergrowth layer, accounting for 90.97%, 1.13% and 790% of total one respectively. Carbon storage of tree in the forest was in obviously dominant position. The average amount of annual fixed carbon of different plantation ages of tree layer, undergrowth layer and died ground cover was 2.043, 0.025 and 0.182 t/hm2 The research shows that carbon density and carbon storage of P. sylvestris var. mongolica plantation varies obviously with forest age, and carbon converges was obvious.