To reveal the effects of salinealkali stress on Toona sinensis seedlings, we treated the potted 1yearold seedlings of _{Toona sinensis} with three alkali levels, A_Ⅰ (pH=7.16), A_Ⅱ (pH=8.47), A_Ⅲ (pH=9.91), and four salt concentrations, S₅₀(50 mmol/L), S₁₀₀(100 mmol/L), S₁₅₀(150 mmol/L), S₂₀₀(200 mmol/L). The photosynthetic parameters, chlorophyll content, membrane damage degree, protective enzyme activity and osmotic regulation substance content under different treatments were examined to provide theoretical basis for developing cultivation of Toona sinensis on saltalkali lands. The results showed that: (1) under A_Ⅰ S₅₀ and A_Ⅱ S₁₀₀ treatments, the aboveground part of Toona sinensis seedlings grew well. (2) With the increases of salt and alkali stress concentration, net photosynthetic rate, transpiration rate, stomatal conductance and chlorophyll content of Toona sinensis leaves were decreased, while the intercellular carbon dioxide concentration appeared increasing. Under the salt concentration of S₅₀ and S₁₀₀, the photosynthetic index of Toona sinensis seedlings treated with A_Ⅰ alkali level did not show significant differences from that of the control (P > 0.05), while the photosynthetic efficiency of seedling leaves decreased significantly under A_Ⅱ and A_Ⅲ levels. Under the salt concentrations of S₁₅₀ and S₂₀₀, each level of alkali treatment significantly inhibited the photosynthetic efficiency in leaves. (3) With the increased salinealkali stress, the relative conductivity, the content of malondialdehyde and the content of proline increased, while the SOD activity, the contents of soluble protein and soluble sugar demonstrated early increase and late decrease. So, the seedlings of Toona sinensis were more sensitive to alkali stress than salt stress, and soil pH is an important factor affecting seedling growth of Toona sinensis. Salinealkali stress significantly inhibited the leaf photosynthesis of Toona sinensis seedlings. However, Toona sinensis can adapt to the salinealkali stress environment by regulating the antioxidant system and osmotic regulation substances, so that it has a certain tolerance to salinealkali conditions.