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In the present experiment, effects of sodium hydrosulfide (NaHS), a H2S donor, on the oxidative damage, antioxidant capacity and the growth of cucumber hypocotyls and radicles were studied under 100 mmol L−1 NaCl stress. NaCl treatment significantly induced accumulation of H2O2 and thiobarbituric acid-reactive substances (TBARS) in cucumber hypocotyls and radicles, and application of NaHS dramatically reduced the accumulation of H2O2 and lipid peroxidation. However, the alleviating effects greatly depended on the concentrations of NaHS, and 400 μmol L−1 NaHS treatment showed the most significant effects. Corresponding to the change of lipid peroxidation, higher activities of antioxidant enzymes as well as the antioxidant capacity indicated as DPPH scavenging activity, chelating activity of ferrous ions and hydroxyl radical (·OH) scavenging activity were induced by NaHS treatment under NaCl stress, especially by 400 μmol L−1 NaHS treatment. With the alleviating lipid peroxidation, the amylase activities in cotyledons were increased, and the length of cucumber hypocotyls and radicles were significantly promoted by NaHS treatment under NaCl stress. Unlike the effects of NaHS, pretreatment with other sodium salts including Na2S, Na2SO4, NaHSO4, Na2SO3, NaHSO3 and NaAc did not show significant effects on the growth of cucumber hypocotyls and radicles. These salts do not release H2S. Based on above results, it can be concluded that the effects of NaHS in the experiment depended on the H2S rather than other compounds derived from NaHS, and the alleviating effects might related with its function in modulating antioxidant capacity and amylase activities.