Abstract: The aim was to investigate the effects of salt stress on radish seedling and its physiological response mechanism, thus to make a preliminary study on salt-tolerance mechanism and screen out salt tolerant cultivars. The seedling growth was studied under artificial medium cultivation with 5 NaCl concentrations (0, 50, 100, 150, 200 mmol/L). With the increase of salt concentration, the seven indexes such as fresh weight of blade and wet weight of above-ground reduced significantly. When the concentration was higher than 100 mmol/L, there were significant differences between control group and treatment group. While with the increase of NaCl concentration, root fresh weight and dry weight increased first and then decreased. Under increased NaCl stress, POD, CAT and SOD in seedling decreased first, and then increased, and decreased finally. The relative chlorophyll content in seed revealed a trend of decrease, while the content of MDA increased. Soluble protein content increased first and then declined rapidly at 200 mmol/L salt concentration. To sum up, the salt stress inhibited radish seedling growth, and the effect of inhibition increased with higher salt stress. Antioxidant enzyme activities and soluble protein content had the function of maintaining the steady structure of cell velum under NaCl stress. Relative chlorophyll content and MDA could reflect the level of salt injury of radish seedling.