In order to study the changes of main oxidase and antioxidase in the pathological scars, the tissues of hypertrophic scar(10 cases), keloid(10 cases) and normal skin(8 cases)were obtained. The concentration of malonaldehyde (MDA) and the activities of xanthine oxidase(XO), copper, zinc-superoxide dismutase(CuZn-SOD)，catalase(CAT) as well as glutathione peroxidase(GPX) were detected by spectrophotometric method. Compared with normal skin tissues, the concentration of malonaldehyde and xanthine oxidase activity were significantly higer in pathological scars (P < 0.05), SOD activity were higher, CAT activity was decreased remarkably in pathological scars than that in normal skin tissues (P < 0.05). And the activity ratios of CAT/CuZn-SOD and GPX/CuZn-SOD were obviously reduced (P < 0.05). However, no significantly differences were observed in the decrease activity of GPX. Differences in above-mentioned indexes all were not remarkable between hypertrophic scars and keloids. These data suggest that the changes of XO, CuZn-SOD, CAT and GPX activities may be a reason resulted in an increase in the level of reactive oxygen species in pathological scars. In the alternative of antioxidants, CAT may be more reasonable.