Abstract: To determine the beneficial effect of cobalt on the growth of Hordeum vulgare under NaCl stress, the effects of addition of CoCl₂ on seed germination, seedling growth, endogenous hormones and some physiological indexes of barley seedlings under NaCl stress were studied. With the aggravation of NaCl stress, the germination vigor, germination capacity, shoot length and root length decreased considerably, while the contents of abscisic acid (ABA) and malondialdehyde (MDA) increased significantly, and the activities of antioxidant enzymes were enhanced. Under NaCl stress, germination vigor, germination capacity, shoot length and root length and the activities of antioxidant enzymes were elevated by the treatment of 0.1 mmol/L CoCl₂, compared with NaCl stress alone, and it dramatically inhibited the accumulation of MDA and ABA. This effect was more significant under the more serious NaCl stress. The results showed that the addition of CoCl₂ could improve (IAA+GA₃)/ABA, enhance the ability to clear up reactive oxygen species, reduce lipid peroxidation under NaCl stress, and promote seed germination, seedling growth and adaptive capacity of barley.