Abstract: The effects of salicylic acid (SA) on the level of reactive oxygen species (ROS) and activities of antioxidative enzymes in Aegilops tauschii roots by 20% PEG6000 were investigated. 20% PEG6000 resulted in significant increase in the contents of O2, H2O2 and MDA and decrease in the activities of superoxide dismutase (SOD), glutathione reductase (GR), catalase (CAT) and ascorbate peroxidase (APX) in Aegilops tauschii roots. However, SA obviously inhibited the increase in the level of MDA and O2- induced by PEG6000 and relieved the effects of PEG6000 on the activities of SOD, GR and CAT. The activities of APX were not obviously changed by SA after treatment PEG. These results suggest that SA may relieve the damage to Aegilops tauschii by altering the activities of SOD, GR and CAT under water deficit.