Abstract: Variations in malondiadehycle (MDA) contents, enzymatic activities and isozymatic patterns of superoxide dismutases (SOD), peroxidases (POD) and catalases (CAT) of leaves at four-leaf stage were studied by treating Vicia faba L. with 3.50mW/mm2 He-Ne laser at different stages. The results indicated that He-Ne laser lead to a significant decrease in MDA contents, with no difference among treatment groups, while enzymatic activities of SOD, POD and CAT were enhanced by different degrees after Vicia faba L. at being treated by He-Ne laser at different stages. In addition, isozymes changes of SOD and POD were observed in groups treated with laser after seeds soaked for 24 h and when embryonic buds emerged, while no change was observed in the group treated at the one-leaf stage. There was no variation in CAT isozymes among different groups. Also, no changes in all three isozymes were observed in the group treated at the one-leaf stage.