Objective：To explore the cell death mechanism in hippocampal CA1 region of rats with global cerebral ischemic injury. Methods：Global cerebral ischemia model was established using bilateral carotid artery occlusion method and samples were acquired at 0，5，10，15，20，25，30 min respectively after model establishment. Model identification was made by TTC staining and brain wa－ter content detection. Morphological changes in hippocampal CA1 region of rats with global cerebral ischemic injury were observed by optical and electron microscopy. Immunohistochemistry and immunoblotting were used to detect the protein expression of poly adeno－sine diphosphate ribose polymerase-1（PARP-1） and Caspase-3 in hippocampal CA1 region of rats. Results：Positive expression of PARP-1 was located in nerve nucleus in hippocampal CA1 region and positive expression of Caspase-3 was located in the cyto－plasm. PARP-1 expressed mildly in hippocampal CA1 region at 0 min（0.023 3±0.035 1），obviously enhanced at 5 min（1.063 3±0.090 7 and continued until 30 min（1.490 0±0.183 3），which was different from that of 0 min（P=0.000）. Caspase-3 expressed neg－atively at 0 min of ischemia and expressed positively at 5 min of ischemia（0.080 0±0.020 0） and lastes for 30 min. there were sta－tistical differences in expression of Caspase-3 at 5 min and 0 min（P=0.006）. Conclusions：Oncosis involves in the cell death of glob－al cerebral ischemic injury and the reason is excessive activation of PARP-1 after ischemic brain injury.