Selecting Threeyearold Phellodendron amurense seedlings in field, we conducted the artificially controlled twofactor randomized block experiment. We analyzed the relative chlorophyll content, gas exchange parameters and carbon and nitrogen stoichiometric characteristics under different light ［full light (S₀), 21.4% light shading (S₁) and 8.7% severe shading (S₂)］ and nitrogen ［no addition control (F₀), light nitrogen addition (F₁) and severe nitrogen addition(F₂)］ stresses, to explore the response mechanism of P. amurense seedlings to shading and nitrogen addition. The results showed that: (1) with the increase of shading, the SPAD value, T_r, G_s, C∶N and PNUE of seedling leaves increased at first and then decreased, and the SPAD value under the two shading conditions were significantly higher than that in full light. P_n, WUE and L_s decreased gradually, while the N and C contents decreased at first and then increased; (2) With the increase of nitrogen addition, P_n, WUE, L_s, N and C contents increased at first and then decreased, while T_r, G_s and PNUE decreased and C∶N increased gradually; (3) There was no significant difference in P_n among different light and nitrogen treatments; SPAD value in the combination of S₁F₀, S₂F₀ and S₁F₂ was significantly higher, while that of full light (S₀) was the lowest. T_r, G_s of light shading (S₁) were significantly higher, while those of S₂F₁, S₀F₂ and S₂F₂ were significantly lower. WUE and L_s were significantly the highest in S₀F₂ and the lowest in S₂F₂ treatment. The N and C contents were higher under heavy shading/light nitrogen addition (S₂F₁), while C∶N and PNUE were higher under light shading/nitrogen zero addition (S₁F₀). (4) According to the comprehensive evaluation of membership function menthod, P. amurense seedlings belonged to moderately resistant type to the light and nitrogen interaction effect. The combination of light and nitrogen suitable for seedling growth was no nitrogen in light shading(S₁F₀) , light nitrogen addition in light shading(S₁F₁) and light nitrogen addition in full light(S₀F₁). The research founded that the light factor is the dominant factor affecting the photosynthesis and regeneration of P. amurense seedlings, but P. amurense could tolerate certain shade stress at the seedling stage. When the light is not limited, the moderate nitrogen addition is beneficial to the growth of P. amurense seedlings; when the light intensity is heavily limited, nitrogen addition inhibits the synthesis of chlorophyll and reduces the light energy utilization efficiency in seedlings, which is not conducive to seedling growth.