Abstract: Effects of exogenous spermidine (Spd) on the physiological characteristics and total flavonoid of Impatiens wallerana Hook. f. under the NaCl (100mmol/L) stress condition were studied. The Impatiens wallerana Hook. f. were cultivated in 0,0.2,0.4,0.6,0.8 mmol/L Spd for 12 days and then the determination of their physiological characteristics and total flavonoid content is carried out. The results showed that the soluble sugar, soluble protein and the activities of SOD, POD, CAT decreased, the content of proline and malondialdehyde(MDA)increased, and the membrane lipid peroxidation intensified under NaCl stress. After the Spd treatment, the content of soluble sugar, soluble protein and proline have all increased, and the activities of SOD, POD, CAT take on an increasing trend; the malondialdehyde content decreased, and the total flavonoids content increased. As a result, Spd could alleviate the damage inflicted by the NaCl stress upon Impatiens wallerana Hook. f., and increase the total flavonoid content, with the best treatment effect observed when treated with 0.6 mmol/L Spd.