 This study aimed to investigate the potential role of reactive oxygen species, ROS, in brain ischemia by evaluating their levels after right middle cerebral artery occlusion, MCAO, and assessing the effects of delayed treatment with ROS scavenger dimethyl theory, DMTU. The results showed that ROS levels increased at one hour after reperfusion and then gradually decreased, reaching their lowest point at three days before increasing again. ROS levels negatively correlated with neurological function scores. Delayed DMTU treatment worsened neurological outcomes, decreased microvessel density, and inhibited stress-activated protein kinase activation, suggesting that ROS may play a biphasic role in cerebral ischemia, inducing damage during the injury phase and participating in recovery. This article was authored by Jipping Yang, Jin Chong Chi, Baoshan Xiu, and others.