Abstract: The callus of barnyard grass (Echinochloa crusgalli)was treated with compound 5 (1-phenyl-4-(3,4-methylenedioxy)-phenyl-diacetylene) under UV-A irradiation for 3 h, which forms an inner environment of oxidizing stress in the cells. Exploiting the method of bioche-mistry, we assay the activity of several protective enzymes in the oxidizing stress. The results showed that compound 5 can stimulate the activity of glutathione-S-transferase(GST), glutathione peroxidase (GSH-Px) and peroxidase(POD) and inhibited the activity of superoxide dismutase (SOD) under UV-A. The activities of GST, GSH-Px, and POD under light were higher than those under non-light. The enhanced percentages of GST, GSH-Px, and POD at the concentration of 10 mg/L under light were 10.47%, 113.68% and 166.68%, but SOD was inhibited at 1 mg/L and 10 mg/L, the inhibiting percentage was 50.25% and 76.46%, respectively. The relationship between compound 5 oxidization and anti-oxidization was discussed in the paper.