[Objective] The study aims to investigate the effects of externally applied methyl jasmonate (MeJA) on the growth and physiological characteristics of Jujube seedlings under salt stress, and to preliminarily analyze the optimal concentration and mechanism of MeJA to improve the salt tolerance of Jujube. [Methods] Taking jujube seedlings as materials, after 150 mmol/L NaCl stress for 10 d, 0, 100, 200, 400, 800 μmol/L MeJA was sprayed to analyze the changes of growth, photosynthetic parameters, and physiological indexes of stress resistance of seedlings under each treatment. [Results] After salt stress , the height, root length and relative water content of Jujube seedlings were suppressed, the chlorophyll content, net photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration rate (Tr) of leaves were reduced, and the inter-cellular CO2 concentration (Ci) was elevated; the activities of antioxidant enzymes SOD, POD and CAT, the content of malondialdehyde, osmoregulatory substances proline, soluble sugar and reducing components flavonoids and polyphenols were elevated. The exogenous MeJA could effectively alleviate the adverse effects of salt stress on the growth and photosynthetic efficiency of Jujube seedlings, and further increase the activities of antioxidant enzymes, osmoregulators and reducing substances, and the degree of alleviation showed a trend of increasing and then decreasing with the increase of the concentration of MeJA, and the best effect was achieved with 200 μmol/L MeJA. [Conclusion] Exogenous MeJA can enhance the photosynthetic efficiency, osmoregulation ability and antioxidant enzyme defense function of Jujube seedlings under salt stress, effectively alleviate the growth inhibition of salt stress, and thus improve the salt tolerance of plants.