Abstract: In order to exploit the salttolerance ability and mechanism of Gleditsia microphylla, the plant growth, cell membrane permeability, the activities of cell protective enzymes, and the distributions of Na⁺ and K⁺ in different tissues were investigated under various NaCl stress (0.053%, 0.15%, 0.3%, 0.45% and 0.6%) with potted twoyear seedlings. The results were as follows: With the increase of NaCl concentration, the seedling growth decreased while the salt injured index increased, and the salttolerance thresholds of seedling was 0.42% NaCl. With the NaCl concentration increasing, the membrane permeability, superoxide anion radical generating rate and MDA content increased grandly, while the activities of SOD, POD and CAT demonstrated an increasedecrease curve which reached the peak at 0.3% or 0.45%. Under the high salt stress condition, the superoxide anion could be consumed timely by increasing the activities of SOD, POD and CAT enzymes, which was useful to avoid cell injure. Under salt stress condition, the Na⁺ content in different tissues increased gradually, following the order of root > leaf > stem, and the K⁺ content and K⁺/Na⁺ in different tissues decreased, following the order of leaf > root > stem. The K⁺-Na⁺ selective transportation coefficients (S_K⁺·Na⁺) of stem and leaf tissues under the soil NaCl stress condition were both increased, following  the order of leaf > stem. In conclusion, the findings suggested that the saltadaptation mechanisms of G. microphylla were root saltrejection by Na⁺ accumulation and restriction in root tissue and leaf salttolerance by a remarkably increased ability of K⁺ selective absorption and accumulation in leaf tissue.