Salt stress is the main type of abiotic stress affecting crop growth, causing ion toxicity and osmotic stress, leading to weakened plant growth, greening, wilting and even death. Previous studies have shown that the appropriate concentration of exogenous spermidine can alleviate the damage degree of plant leaves under salt stress conditions, enhance the ability of biofilm to resist salt ion damage, and promote plant growth. The experiment adopted nutrient solution culture method to simulate different salt stress levels with 100mmol·L-1, 200mmol·L-1 and 300mmol·L-1 NaCl solutions. And the medium salt-tolerant variety Jinshu 16 and the mild salt-tolerant variety Jizhangshu 12 were used as test materials. When the virus-free potato seedlings reach 4~5 true leaves, continuous foliar spraying of 0.9 mmol·L-1 exogenous spermidine was applied for 7 day, 2 times per day. The effects of exogenous spermidine (Spd) on the growth of potato seedlings, the activity of antioxidant enzymes and the content of osmotic regulatory substances in leaves were analyzed. The results showed that: (1) Leaf spraying Spd alleviated the inhibitory effect of salt stress on seedling growth, increased chlorophyll content and root activity, and increased the activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), ascorbate (ASA) and glutathione (GSH). And proline, soluble sugar, amino acid content; (2) Under 200 mmol· L-1NaCl stress, Spd had the most significant alleviating effect on "Jinshu 16". Studies have shown that Spd can improve the adaptability of potato seedlings to salt stress and promote the growth of potato seedlings by improving the root vitality, chlorophyll content, antioxidant enzyme activity and osmotic regulation ability of potato seedlings.