Effects of moderate (200 mmol/L NaCl) and severe (400 mmol/L NaCl) salt stress on the growth characteristics of Sophora alopecuroides were studied by measuring gas exchange, chlorophyll fluorescence parameters and growth indexes. The results showed: (1) one day after moderate salt stress, significant decreases were measured in photosynthetic rate (P_n), stomatal conductance (G_s), transpiration rate (T_r) and intercellular carbon dioxide concentration (C_i) of S. alopecuroides seedlings. Five days after moderate salt stress, slight decrease occurred in P_n while slight increase was measured in C_i. However, one day after severe stress, significant decreases were measured in gas exchange of S. alopecuroides, with it getting worse along with longer time stress. The reason for the decrease of photosynthetic rate of S. alopecuroides was due to the combined effect of stomatal factors and nonstomatal factors. The decrease of P_n was mainly caused by nonstomatal factors under severe salt stress. (2) The maximum photochemical efficiency (F_v/F_m), photochemical quenching coefficient (qP), actual photochemical efficiency (Φ_PSⅡ) decreased in different levels. The decrease was more significant in severe salt stress than in moderate salt stress treatment. The change of fluorescence parameters was not obvious under moderate salt stress, while it was significant under severe salt stress along with the prolongation of stress time. (3) With the aggravation of salt stress, water content and growth indicators (plant height, root length, dry weight) were markedly decreased, leading to a serious inhibition in plant growth. The results showed that the tolerability of halophytes to salt stress was also limited. The growth of S. alopecuroides was slightly inhibited under 200 mmol/L NaCl stress while it was seriously damaged under 400 mmol/L NaCl stress.