Abstract: The effect of CO₂ enhancement, nitrogen deposition and their interaction on the northern boundary (Zhuanghe in Liaoning Province) of Quercus variabilis seedlings was studied by controlling the CO₂ concentration (700 μmol·mol^-1; 400 μmol·mol^-1) and nitrogen level (non nitrogen fertilizer: CK; nitrogen fertilizer: 120 kg N·hm^-2). The results showed that under elevated CO₂, the Q. variabilis seedlings’ leaf morphology, photosynthetic pigments and leaf nitrogen content tended to decrease, and the dark respiration rate decreased 63.3% and soluble sugar increased 2.6%. Nitrogen deposition significantly promoted the Q. variabilis seedlings’ leaf morphology and photosynthetic pigments, leading to increased leaf nitrogen content, decreased potassium content, and 26.7% of increase in nitrogen to potassium ratio. CO₂ and N interaction played a significant role on promoting the Q. variabilis seedlings’ leaf morphology and photosynthetic. The maximum net photosynthetic and light saturation point were 1.4 and 2.6 times of the control, while dark respiration and light compensation point decreased 65.9% and 50.0%, respectively. Elevated CO₂ and nitrogen deposition had a positive effect on Q. variabilis seedlings to some degree, which might result in the movement of distribution boundary of Q. variabilis to north.