Photosynthetic nitrogen-use efficiency (PNUE), which is defined as the ratio of light-saturated photosynthesis (A_max) to nitrogen concentration in a defined leaf area (N_area), is considered an important trait for characterizing species regarding their leaf economics, physiology, and strategy. The light environment may influence photosynthetic capacity and leaf nitrogen content, and may also influence biochemical factors that affect PNUE such as nitrogen allocation to the photosynthetic apparatus, CO₂ diffusion from the atmosphere to the site of carboxylation, and specific activity of the photosynthetic enzymes. The objective of this study was to describe the inherent PNUE variation in leaves of Manglietia glauca seedlings grown under varying light environments. An improved understanding of this process is of great importance for M. glauca seedling cultivation and artificial pure forest modification. The results showed that A_max of M. glauca seedlings grown under 60% shade (6.03 μmol m^-2 s^-1) was higher than that under other shading levels, mainly because of a higher maximum carboxylation rate (32.93 μmol m^-2 s^-1) and a higher maximum electron transport rate (61.83 μmol m^-2 s^-1). Thus, moderate shading may assist in the cultivation and planting of M. glauca seedlings because A_max improvement could significantly enhance their growth rate. No significant differences were observed in intercellular and chloroplast CO₂ concentrations in M. glauca seedlings grown under different shading levels. Mesophyll conductance and stomatal conductance of M. glauca seedlings grown under 90% shade were lower than those under other shading levels. No significant difference was observed in the PNUE of M. glauca seedlings grown under different shading levels, because N_area changed synchronously with A_max, which was largely attributed to the lack of significant difference in the proportion of total leaf nitrogen allocated to Rubisco and bioenergetics in such seedlings. Shading significantly enhanced the proportion of total leaf nitrogen allocated to light-harvesting machinery (P_L) in the following order:90% shade (0.296 g/g) > 60% (0.216 g/g) > 0 (0.132 g/g). However, enhanced P_L under increased shade did not improve the PNUE. The proportion of total leaf nitrogen allocated to the photosynthetic apparatus (P_P) was higher than that allocated to the cell wall (P_CW); for M. glauca seedlings grown under 0, 60%, and 90% shade:P_P was, respectively, 3.3, 5.8, and 6.0 fold higher than that of P_CW. The P_P of M. glauca seedlings grown under 90% shade was higher than that observed under 60% shade, and the lowest P_P was observed under 0 shade. No significant difference in P_CW was observed in seedlings grown under the different shading levels. The proportion of total nitrogen allocated to other plant organs (1-P_P-P_CW:P_Other) was higher than P_P and P_CW under all shading levels in the following order:0 shade (0.755 g/g) > 60% (0.683 g/g) > 90% (0.596 g/g). The relatively high P_Other under all shading levels implied sufficient nitrogen supply in the leaf for Rubisco, bioenergetics, light-harvesting machinery, and the cell wall. Thus, there was no relative change in the proportion of total nitrogen allocated to these components, and the P_L increase was attributed to other nitrogen pools. In conclusion, for artificial pure forests where M. glauca seedlings are planted, forest gaps should be restricted, because the species is adapted to a moderately shaded light environment. In addition, when subject to shading, M. glauca seedlings should receive additional nitrogen to replenish leaf nitrogen consumption.