Objective：To study that the effect of different sevoflurane treatments on level of oxidative stress for thoracic surgery pa－tients with one lung ventilation（OLV）. Methods：Totally 80 patients undergoing thoracic surgery with OLV were randomly divided in－to four groups：propofol group（P group），sevoflurane pretreatment group（S1 group），sevoflurane aftertreatment group（S2 group） and sevoflurane whole-treatment group（S3 group）. Anesthesia of four groups was inducted with propofol. In P group，anesthesia was maintained with infusion of propofol and remifentanil. Anesthesia was treated for 30 min before OLV in S1 group and after OLV in S2 group. The patients in S3 group were treated for whole-progressing with 1.0 MAC sevoflurane. Blood samples were taken from radial artery before induction of anesthesia（baseline T0），before OLV（T1），at 30 min after OLV（T2） and at 24 h after OLV（T3）. Meanwhile，bronchoalveolar lavage fluid was taken at T1 and T2. The content or activity of malondialdehyde（MDA），superoxide dismutase（SOD），lactate dehydrogenase（LDH） and nitric oxide（NO） in serum and bronchoalveolar lavage fluid were determined with chemical colori－metric method. Results：The levels or activity of MDA，SOD，LDH and NO in serum in each group were significantly increased at T2 and T3 than at T0 and T1（P<0.05）. But the levels of MDA，LDH and NO were significantly decreased and the activity of SOD were obviously increased in S1-3 groups than in P group（P<0.05），and there was no significant difference among S1，S2 and S3 groups（P >0.05）. After OLV 30 min（T2），the levels or activity of MDA，SOD，LDH and NO in serum in four groups were sig－nificantly increased at T2 and T3，compared with those at T0 and T1（P<0.05）. But the levels of MDA，LDH and NO were significantly decreased and the activity of SOD were obviously increased in S1-3 groups than in P group（P<0.05），and there was no significant dif－ference in S1，S2 and S3 groups（P>0.05）. Conclusion：Different sevoflurane treatments can decrease the content of MDA，LDH and NO，and increase the activity of SOD in serum and bronchoalveolar lavage fluid. The results suggest that sevoflurane possess potential for anti-oxidative stress injuries.