Using one-year-old Gymnocarpos przewalskii seedlings as materials, the leaves of G. przewalskii seedlings were treated with 0.4%, 0.8%, 1.2% and 1.6% NaCl solution under potted conditions, and the activities of antioxidant enzymes and contents of osmotic regulatory substances were measured under each NaCl treatment. Chlorophyll content, relative electrical conductivity, malondialdehyde (MDA) content, plant height, base diameter, root, stem, leaf, total dry weight, root-shoot ratio, to investigate the physiological tolerance to salt stress of G. przewalskii seedlings. The results showed as follows: (1) With the increase of salt stress, plant height, base diameter, root dry weight, stem dry weight, leaf dry weight and total dry weight showed a decreasing trend, while the root-shoot ratio showed an increasing trend. The seedling height, base diameter and root dry weight did not change significantly under 0.4%NaCl treatment, but the stem dry weight, leaf dry weight and total dry weight were significantly lower than the control under each NaCl treatment. (2) With the aggravation of salt stress, the contents of soluble sugar (SS), soluble protein (SP), superoxide dismutase (SOD) and peroxidase (POD) activities in leaves of G. przewalskii seedlings were firstly increased and then decreased; While proline (Pro) content, catalase (CAT) activity, relative conductivity (REC) and MDA contents all showed an increasing trend. Under 0.8%NaCl treatment, SS and SP contents decreased, SOD and POD activities decreased, REC and MDA contents increased significantly, which severely inhibited the synthesis and accumulation of dry matter. (3) With the aggravation of salt stress, the content of chlorophyll a, chlorophyll b, chlorophyll a+b and carotenoid in the leaves of G. przewalskii seedlings decreased significantly. The comprehensive analysis showed that the growth of G. przewalskii seedlings was inhibited to different degrees under salt stress. The leaves of G. przewalskii could adapt to the salt stress environment by regulating osmotic regulatory substances and antioxidant system, and thus had a certain ability of salt tolerance. When NaCl concentration exceeds 0.4%, the growth is significantly inhibited, osmotic regulation and antioxidant capacity are weakened, and the membrane system is obviously damaged.