To explore the protective effects of Danhong injection against cerebral damage during on-pump coronary artery bypass graft surgery and its mechanism. Methods. Fifty patients scheduled for on-pump CABG surgery were randomly divided into Danhong injection group (group D) and control group (group C). Group D was given Danhong injection while group C was given the same volume of normal saline when the artery was cut open. Jugular bulb blood right before the operation began (T1), when body temperature rewarming to 36°C (T2), 30 min after the termination of cardiopulmonary bypass (T3), and 6 hrs after the termination of CPB (T4) was collected. The superoxide dismutase activity by using xanthine oxidase method and concentration determination of malondialdehyde were examined. Results. In group C, SOD activity was less at T2-T4 than at T1. It was also less active comparatively in group D at T2-T4. The MDA concentration increased in both groups but was more obvious in group C. Levels of TNF-α, IL-6, IL-8, and IL-10 increased in both groups C and D at T3 and T4, compared to T1. Conclusions. Danhong injection shows significant protective effects against cerebral damage during on-pump coronary artery bypass graft surgery.