Abstract:This paper studied the effects of foliar spraying spermidine and sperm ine on the leaf antioxidant system of Celastrus orbiculatus under soil NaHCO 3 stress. The results showed that under the stress, spraying spermidine and sp ermine could significantly decrease the leaf O2〖SX(B-*3〗-〖〗·〖SX)〗 production rate, H2O2 and MDA contents, and electrolyte leakage of C. orbiculatus (P<005). Spra ying spermidine increased the leaf SOD, CAT, POD and APX activities and GSH, CAR and Pro contents obviously, but had no effect on leaf AsA content. Spraying sp ermine also increased leaf POD and APX activities and GSH, CAR and Pro contents obviously, but had lesser effect on leaf SOD activity and AsA content, and even , caused a significant decrease in leaf CAT activity. In the meantime, spermidin e and spermine effectively improved the growth of C. orbiculatus seedlings. It was suggested that under soil NaHCO3 stress, exogenous spermidine and sperm ine could improve the functions of membrane protective system and decrease the O 2〖SX(B-*3〗-〖〗·〖SX)〗 accumulation in C. orbiculatus leaves, an d consequently, increase the C. orbiculatus tolerance to NaHCO3 exposure.