To study the effects of exogenous salicylic acid (SA) on salt tolerance physiology of Ulmus pumila seedlings under NaCl stress, we explored the effects of 0, 0.5, 1.0 and 2.0 mmol·L^-1 SA on the photosynthetic rate and ion distribution of annual U. pumila seedlings under different NaCl concentrations (0, 50, 100 and 150 mmol·L^-1). The results showed that: (1) NaCl stress significantly inhibited the growth and photosynthetic capacity of U. pumila seedlings, and the ion balance was destroyed. (2) After spraying exogenous SA, the dry weight and rootshoot ratio of U. pumila seedlings increased in varying degrees. 0.5 and 2.0 mmol·L^-1 SA improved the chlorophyll and carotenoids pigment contents in leaves of U. pumila seedlings under 50 and 100 mmol·L^-1 NaCl stress． (3) The net photosynthetic rate (P_n), stomatal conductance (G_s) and transpiration rate (T_r) of U. pumila seedlings significantly increased with the addition of 0.5 mmol·L^-1 SA under 50 mmol·L^-1 NaCl treatment. And 1.0 and 2.0 mmol·L^-1 SA have better improvement effect on the net photosynthetic rate (Pⁿ) of seedlings under 150 mmol·L^-1 NaCl, while the exogenous SA had no significant effect on the photosynthetic parameters under 100 mmol·L^-1 NaCl. (4) The content of Na⁺ and the ratios of Na⁺/K⁺, Na⁺/ Ca²⁺, Na⁺/ Mg²⁺ in leaves and roots of U. pumila were reduced by using exogenous SA under salt stress, while the ionselective transport coefficients S_K，Na, S_Ca，Na and S_Mg，Na were increased which promoted the transfer of K⁺, Ca²⁺, and Mg²⁺ from roots to leaves. Membership function analysis found that the SA concentrations with the best improvement effect on the ion content in leaves and roots of U. pumila were 1.0 and 2.0 mmol·L^-1, respectively. Therefore, appropriate concentration of exogenous salicylic acid can improve the photosynthetic capacity and regulate the ion state of U. pumila seedlings effectively under NaCl stress, thus enhancing the resistance of U. pumila to NaCl stress.