Objective To study carbon (C) content, storage and allocation in seedling organs of Cinnamomum camphora cultivated in four different densities under nitrogen (N) and phosphorus (P) additions, and provide information for forest C storage and allocation under the background of N deposition and P addition.Method The 1-year-old C. camphora seedlings were used as test materials. NH₄Cl and NaH₂PO₄·2H₂O were selected to simulate atmospheric N deposition and P addition, respectively. N and P additions were performed with four different levels (control, N, P, and N+P). The N and P addition amounts per year in N, P, and N+P treatments were 40 g·m^-2 NH₄Cl, 20 g·m^-2 NaH₂PO₄·2H₂O and 40 g·m^-2 NH₄Cl + 20 g·m^-2 NaH₂PO₄·2H₂O, respectively. Seedlings were planted in four different densities (10, 20, 40 and 80 seedlings·m^-2).Result C contents in roots, stems and branches of seedlings in all treatments had no significant difference. N and N+P treatments increased C content of leaves. With the increase of planting density, C content of leaves tended to decrease. The N and P additions increased C storage per seedling and C storage in unit area. C storage per seedling decreased with the increase of planting density.Conclusion C storage of leaves per seedling and C storage in unit area decreases with the increase of planting density. C storage percentage of stems increases in high cultivation density treatment. The effect of N+P treatment on C storage per seedling and C storage in unit area is greater than that of single N or P addition.