Abstract: 【Objective】The study aimed to investigate the alleviating effect of H2S on growth inhibition of cucumber seedlings under salt stress,providing scientific basis for cucumber salt-tolerant cultivation.【Method】Cucumber cultivar Xinchun No.4 was employed as the materials,which was water-cultured and NaCl （50 mmol/L） stressed in climatic chamber;and the leaves were sprayed with H₂S donor （i.e.,NaHS）of 200μmol/L and H₂S synthesis inhibitor PAG （DL-propargyl glycine,150μmol/L）.【Result】Compared with the NaCl stress,the foliar spraying with NaHS could improve the growth of cucumber seedlings,the dry masses of above ground and underground increased by 29.12%and 48.52%,respectively;and the contents of soluble sugar and proline increased by 53.99%and 22.21%,and also,the content of photosynthetic pigment and chlorophyll fluorescence parameter F_v/F_m significantly increased.The contents of hydrogen peroxide （H₂O₂） and malondialdehyde （MDA） decreased by 37.79%and 24.27%,respectively,and the antioxidant enzymes activity also decreased,while these indexes exhibited the opposite change in the PAG-treated cucumber seedlings.【Conclusion】H₂S can increase the accumulation of osmotic regulatory substances,mitigate the loss of photosynthetic pigments,maintain the maximum photochemical efficiency of PSII,regulate the activity of antioxidant enzymes,and alleviate the damage of oxidative stress to cucumber seedlings under moderate salt stress,and whereby improve salt tolerance of cucumber plants.