Objective：To investigate glutathione peroxidase，superoxide dismutase and malondialdehyde concentration in gingival crevicular fluid in patients with human peri-implantitis and to provide the basis for diagnosis and adjunctive treatment for peri-im－plantitis. Methods：Peri-implant sulcular/gingival crevicular fluid（GCF） samples were collected from sixty-two patients loaded more than one year. The experiment was divided into 4 groups：peri-implantitis group（PI，n=15），health implant group（HI，n=66），tooth in peri-implantitis group（TPI，n=15），tooth in health implant group（THI，n=66）. After the clinical measurements（probing depth，gingival index，gingival bleeding index，plaque index），GCF samples were collected. Then glutathione peroxidase，superoxide dismutase，malondialdehyde and IL-1β were analyzed by enzyme-linked immunosorbentassays. Results：PLI，PD，mBI，IL-1β and gingival crevic－ular fluid in PI group（2.20±0.78，4.63±0.92，2.60±1.12，21.07±2.29，1.34±0.17） were higher than those of HI group（1.03±0.89，1.76±0.73，1.14±0.97，18.79±2.07，0.83±0.23），（P=0.000，0.000，0.001，0.000，0.000） and TPI group（1.13±0.92，1.53±0.72，1.00±0.93，18.52±2.37，0.74±0.26）（P=0.011，0.000，0.001，0.000，0.000）.SOD and GP-x concentrations were lower in PI group（218.65±16.27，178.66±21.77） than in HI group（243.52±19.71，211.96±21.43）（P=0.000，0.000）and TPI group（230.63±26.91，213.04±25.75）（P=0.016，0.000）. No difference was observed in PLI，PD，mBI，IL-lβ，SOD，GP-x，and gingival crevicular fluid in THI group and HI group. No difference in MDA was observed among all groups. Conclusion：Oxidative stress may play a role in the inflammation and destruction of the implant periodontium in peri-implantitis.