Abstract: Carbon and nitrogen characteristics of Pinus koraiensis seedling and its soil under different CO₂ concentrations were investigated to explore the response strategies of P. koraiensis and their habitats to higher CO₂ concentration conditions. Based on growth chamber method, the concentration and accumulation of carbon and nitrogen in P. koraiensis seedling organs and its soil were measured and compared under environmental CO₂ concentration of 350 μmol/mol and 700 μmol/mol, respectively. Comparing to lower CO₂ concentration of 350 μmol/mol after a growth season, the results showed that: ① No significant difference of carbon concentration was detected in root, stem and leaf of P. koraiensis seedling by CO₂ treatments, however carbon accumulation of the leaf increased by 37.63% when CO₂ concentration increased to 700 μmol/mol. ② Nitrogen concentration of root, stem and leaf decreased significantly at higher CO₂ concentration, and the stem nitrogen accumulation to CO₂ enrichment declined by 27.45%. ③ C/N ratio of root, stem and leaf to CO₂ enrichment increased significantly. ④ Concentration of soil extractable dissolved organic carbon increased significantly by 28.82% at higher CO₂ condition, the concentration of soil organic carbon, microbial biomass carbon, soil total nitrogen, microbial biomass nitrogen and hydrolysable nitrogen did not change significantly between CO₂ treatments, and soil C/N ratio to CO₂ enrichment varied with a small increasement. Overall, nitrogen concentration, C/N ratio, leaf carbon accumulation of P. koraiensis seedling and soil extractable dissolved organic carbon responded quickly to higher CO₂ concentration during this period.