In this study,changes of activity of antioxidant enzyme of earthworm in vegetable greenhouse in Chifeng after infected by Trichlorfon were detected.The results showed that Trichlorfon have an impact on superoxide dismutase（SOD）,peroxidase enzyme（POD） and glutathione peroxidase（GSH-px） activity of earthworm.SOD and POD activity showed a similar tendency,i.e.,increased at first and then declined.POD activity increased at lower trichlorfon concentrations than SOD activity.The trichlorfon inhibited the activity of GSH-Px.Under The stress of trichlorfon,SOD,POD,GSH-Px of earthworms responded differently.Effect of trichlorfon on SOD was the greatest,followed by POD,and GSH-Px was the minimum.