Objective:To study on protective effect and antioxidative mechanism of preventive moxibustion in rats with adjuvant arthritis（AA）.Methods:Preventive moxibustion was applied at Dazhui（GV 14） in AA rats

and the histopathological changes of the joints

the activity of superoxide dismutase（SOD） and malondialdehyde（MAD） content in hypothalamus and plasma were investigated in the rats at the early and secondary stages.Results:As compared with the normal group

primary synovitis of the ankle joint was more obvious in the various AA groups

and at the secondary stage

the articular cartilage showed a part of injury.SOD activities decreased and MDA content increased in plasma and hypothalamus of the various AA groups（P<0.05 or P<0.01）.The preventive moxibustion could improve significantly histipathological changes of the primary ankle joints

increase the activities of SOD in plasma and hypothalamus（P<0.05 or P<0.01） and decrease MDA level in plasma （P<0.05） and the hypothalamus（P<0.01） of AA rats at the secondary stage （P<0.01）

but did not significantly change MDA level in the hypothalamus（P>0.05） at the early stage

as compared with the various AA groups at the same stage.The preventive moxibustion could significantly increase plasma SOD activity in the normal rat（P<0.05）.Conclusion:Preventive moxibustion has protective action of inhibiting and relieving primary arthritis at the early and secondary stages in AA rats

and this action is possibly related with preventive moxibustion regulating metabolism of free radicals in blood and the hypothalamus at the early and secondary stages.