Objective:To observe the levels of SOD MDA of brain homogenate and the number of apoptotic neurons, investigate the mechanism for the protective effect of Xingnaojing injection on cerebral ischemia reperfusion injury in ratsMethods: The focal cerebral ischemia and reperfusion model was made by middle cerebral artery occlusion (MCAO). The rats were randomly assigned to 13 groups: sham operated group(n=4), Xingnaojing groups and control groups distinguish by different reperfusion time: 2 hours, 4 hours, 8 hours, 24 hours, 48 hours, 72 hours. Eight rats for each group .Rats in Xingnaojing groups were injected Xingnaojing (1ml/100g/day) into abdominal cavity as soon as ischemia;meanwhile ,rats in control groups were injected with the same dose of saline into abdominal cavity. Half part of rats for each group were selected to detect the levels of SOD and MDA. Others were selected to detect the number of apoptotic neurons by terminal-deoxynucleotidyl transferase medicated nick end labeling (TUNEL)Results:During the experiment ,6 rats were excluded because of dying, but another 6 rats were selected . So that 100 rats were involved in the result.1 During the ischemia reperfusion MDA content of brain homogenate increased and SOD activity of brain homogenate decreased . Xingnaojing can significantly inhibite the increase of MDA after cerebral ischemia reperfusion. Xingnaojing also inhibited the decrease of activity of SOD in rats.2 The number of apoptotic neurons in Xingnaojing groups were significantly lower than that in control groups . The number of apoptotic neurons increased significantly along with the increasing time of ischemia reperfusion .Conclusion:Xingnaojing had protective effects against focal cerebral ischemia reperfusion injuries maybe lie in decreasing cerebral oxygen free radical (OFR) lipid peroxidation and inhibiting neuronal apoptosis.