The pyrogallol autoxidation method used for superoxide dismutase measurement has been improved by using DTT or Vit C as a terminating agent.The reaction system consists of 50mmol/L Tris-HCl,1mmol/L diethylene-triaminepentaacedic acid,0.2mmol/L pyrogallol, pH 8.20 at 25 ℃ in a total volume of 9ml, one drop(about 50μl)of DTT (100mmol/L)or ascorbic acid (5%) being added to stop the autoxidation reaction.The absorbence at 420nm of the reaction system after terminating the reaction keeps constant for an hour.