[Objective]Soil organic carbon (SOC) not only helps to maintain soil health, but also plays an important role in regulating global climate change. At present, the effects of nitrogen (N) and phosphorus (P) additions on soil aggregate carbon and their underlying mechanisms are still unclear. To reveal the effect of N/P addition on soil aggregate carbon in subtropical evergreen broad-leaved forests and its internal mechanism is of great significance for understanding soil organic carbon stability and ecosystem carbon cycle in subtropical evergreen broad-leaved forests. [Methods]N and P addition test platforms were set up in evergreen broad-leaved forest for 6 years (control, 100 kg N hm-1 a-1，50 kg P hm-1 a-1，100 kg N hm-1 a-1+50 kg P hm-1 a-1). The response of soil organic carbon with different particle sizes to N deposition and P addition was investigated by analyzing the particle size classification, phosphorus composition and molecular structure of organic carbonation. [Results] Nitrogen (N) addition significantly increased the content of soil organic carbon (SOC) in macroaggregates (>2 mm) and clay and silt particles (<0.053 mm), and significantly reduced the degree of soil organic carbon decomposition (SD) in macroaggregates (>2 mm) and small aggregates (0.25-2 mm). The combined application of nitrogen and phosphorus (N+P) significantly increased the content of polysaccharides and alcohols and phenols in macroaggregates (>2 mm), significantly reduced the degree of soil organic carbon decomposition (SD) in small aggregates (0.25-2 mm), and significantly increased the content of resin (Resin-P) in soil easily degradable phosphorus of various particle sizes except microaggregates (0.25-0.053 mm). Redundancy analysis showed that NaOHs-Pi and residual phosphorus were the main drivers of the chemical molecular structure of >2 mm and <2 mm aggregates, respectively. [Conclusion] N deposition accelerated soil C sequestration by enhancing the formation of refractory state P and thus the stability of the chemical molecular structure of soil aggregates.