Objective：To study the intervention effect of S-adenosyl-L-methionine（SAM） on oxidative stress in rats with autoimmune emphysema. Methods：Thirty SD male rats with age of ten weeks were randomly divided into three groups：the normal control group（n=10），the emphysema group（n=10） and the SAM group（n=10）. Rats in the emphysema group and the SAM group were treated with intraperitoneal injection of human umbilical vein endothelial cells plus complete Freund’s adjuvant to establish autoimmune emphy－sema models，while in the normal control group were treated with intraperitoneal injection of the same dosage complete Freund’s adju－vant. In addition，rats in the SAM group were also treated with intraperitoneal injection of SAM of 15 mg/（kg·d）. After 21 days，tissue sections of right lung were stained by hematoxylin eosin（HE），pathological changes were observed，and mean linear intercept（MLI） and mean alveolar number（MAN） were measured. At the same time，malondialdehyde（MDA），superoxide dismutase（SOD），activities of glutathione peroxidase（GSH-Px），and the glutathione（GSH） in serum were detected by the spectrophotometry. Levels of anti-endothelial cell antibody（AECA） in serum were detected by using ELISA. Results：MLI in the emphysema group was higher than that in the normal control group，MAN in the emphysema group was lower than that in the normal control group，while MLI and MAN in the SAM group were both in the middle when com－pared with those two groups，with statistically significant differ－ences（P=0.000；P=0.000）. GSH concentration，SOD activity，and GSH-Px activity in the emphysema group were decreased than those in the normal control group（P=0.000；P=0.000；P=0.000），while in the the SAM group were in the middle when compared with those two groups（P=0.000）. MDA concentration in the emphysema group was higher than that in the normal control group，while in the SAM group were in the middle when compared with those two groups（P=0.000）. Conclusion：SAM may inhibit the for－mation of autoimmune emphysema in rats by increasing the production of GSH concentration，SOD activity，and GSH-Px activity，and decreasing the level of MDA.