As one of common pioneer plants growing on mine tailings in Yunnan Province, Rumex dentatus has generated metal tolerant ecotype and could therefore be treated as an ideal experimental material for stress ecology study. To study the roles of different antioxidant enzymes in tolerance mechanism of pioneer plant early-stage seedling to stress, the variation characteristics of antioxidant enzymes of R. dentatus seedlings, sampled from Pb/Zn mine tailings in Lanping, Yunnan Province, were then investigated under exposing to different concentrations of Pb or Zn (0, 1, 5, 10, 50, 100, 200 mg/kg) for 48h in the laboratory. Our results showed that, with the increase of pollutant concentrations, (1) the content of malondialdehyde (MDA) went up sustainably, and had significantly increased respectively to 427% and 330% under the concentrations of 200 mg/kg Pb or Zn when compared with normal control; whereas (2) the activity of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) varied to different extents. Specifically, SOD increased initially but decreased afterwards, and POD increased sustainably; whereas the activity of CAT could neither be detected under Zn stress nor effectively estimated under Pb stress. Subsequent correlation analyses suggested that the antioxidant enzymes have produced some protective effect in the tolerance reaction against Pb and Zn pollution, among which POD has plausibly played the central role.