[Objective] In order to further enhance the role of China′s poplar plantation in achieving the China′s dual carbon goals, the impact of nitrogen addition on the carbon storage allocation pattern of southern poplar plantation was quantitatively analyzed, and theoretical support was provided for the optimization of production and management mode and technology integration of poplar plantation in the new era of China′s dual carbon goals. [Methods] Based on the long-term nitrogen addition plot of poplar plantation in Dongtai Forest Farm, five nitrogen treatments with different concentrations, N0[0 g/ (m²·a) ], N1[5 g/ (m²·a) ], N2[10 g/ (m²·a) ], N3[15 g/ (m²·a) ], N4[30 g/ (m²·a) ], were set in random block groups. The effects of long-term nitrogen addition on carbon storage in tree layers, soil layer, litter layer and understory layer of poplar plantation were studied. [Results] (1) Compared with the control, the carbon storage of poplar plantation significantly increased under the treatments of N3 and N4, and most significantly increased by 21.6%;under the treatment of N3. (2) All treatments significantly increased soil carbon storage in 0—15 cm soil layer, but had no significant effect on soil carbon storage in 30—45 cm soil layer. (3) N2, N3 and N4 had significant effects on litter carbon storage, and N3 had the strongest effect, increasing by 49.7%. All treatments reduced the carbon storage of understory vegetation layer, but the difference was not significant. (4) Correlation analysis showed that the carbon storage in each layer of poplar plantation was positively correlated with TN, MBN, DON and DOC in soil, and negatively correlated with pH and C/N. [Conclusion] Under N3 treatment, 15 g/ (m²·a), had the greatest effect on carbon storage in Dongtai poplar plantation, which was conducive to the rapid and stable accumulation of carbon storage in the ecosystem. [ABSTRACT FROM AUTHOR]