Abstract: In order to learn the contribution of forest ecosystems of Dagangshan National Nature Reserve in Jiangxi Province in reducing the greenhouse effect, nine plots (each 20 m × 20 m) were sampled to investigate the biomass and soil bulk density of three typical subtropical evergreen broad-leaved forests including Castanopsis eyrei, Schima superba, Cyclobalanopsis glauca in 2015 and 2020. The carbon density and carbon storage of vegetation and soil were calculated according to the organic carbon content of vegetation and soil. The changes in carbon sequestration capacity of three typical subtropical evergreen broad-leaved forests in 2015 and 2020 were analyzed. The results showed that the average carbon density of the forest vegetation layer had increased from 89.95 t/hm² in 2015 to 105.29 t/hm² in 2020, of which the arbor layer had increased from 85.97 t/hm² in 2015 to 104.02 t/hm² in 2020, while the shrub layer, herbaceous layer and litter layer was lower in 2020 than in 2015. The average carbon density in soil both decreased with the increasing soil depth, but it’s higher in 2015 than in 2020. The forest average carbon storage in the sampled plots decreased from 12 113.92 kg in 2015 to 11319.84 kg in 2020 with a decrease of 6.56%, of which 3 598.00 kg stored in vegetation in 2015 and 4 211.60 kg in 2020, while the average soil carbon storage decreased from 8 515.92 kg in 2015 to 7 108.24 kg in 2020 with a decrease of 16.53%. The total soil carbon storage in 2020 was 1.69 times that of vegetation (4 211.60 kg), while it was 2.37 times in 2015.