The physiological response characteristics and salt tolerance diversity of four kinds of Fraxinus were studied under salt stress to provide scientific basis for the selection of landscaping tree species in salinealkali land. A 28day hydroponic experiment was conducted with oneandahalfyearold seedlings of Fraxinus velutina, F. pennsylvanica, F. americana and F. chinensis as materials. Their morphology, growth, membrane permeability, antioxidant enzyme activity, chlorophyll content and photosynthetic parameters under NaCl treatments of four concentrations (0, 40, 80, 120 mmol/L) were measured and comprehensively analyzed and evaluated by correlation analysis, principal component analysis and membership function method. The result showed that：(1) under salt stress, the morphological characteristics, relative plant height and growth of four species were inhibited. Membrane permeability and malondialdehyde (MDA) content increased with the raising of salt concentration, while chlorophyll content decreased. (2) With the rising salt concentrations, the activity of POD in leaves of Fraxinus plants first increased and then decreased, with its peak appeared at 40 or 80 mmol·L^-1, though SOD enzyme activity showed different fluctuations. (3) Average net photosynthetic rate (P_n) of leaves of four species decreased with the rising NaCl concentration, in which the rate of F. velutina decreased gently. Intercellular CO₂ concentration (C_i), stomatal conductance (G_s) and transpiration rate (T_r) were changed with no obvious regularity. (4) The comprehensive evaluation of salt tolerance of these four species reached the following conclusions: F. velutina > F. americana > F. pennsylvanica > F. chinensis which shares the same tendency of the morphologic symptoms of salt damage. Therefore, F. velutina and F. americana can be the main experimental materials for stress resistance breeding and be the important species for afforestation in salinealkali land in coastal areas of China.