Abstract： Objective To observe the effects of exogenous sodium phosphocreatine (PCr) on cerebral repeffusion injury of rats after ischemia in order to explore the potential mechanism. Method Thirty-six healthy adult male Wistar rats with body weight 200- 220 g were randomly (random number) divided into sham operation group, ischemic reperfusion (I/R) group and PCr treatment group. The I/R model was established by using electro-cauterizing bilateral vertebral arteries and occluding bilateral common carotid arteries with atraumatic carotid clasps for 10 min, and then the clasps were released for 48 hours reperfusion. In sham operation group, bilateral common carotid arteries were exposed without occlusion. In PCr treatnent group, PCr in dose of 150 mg/kg was administered intravenously 60 min before the occlusion of bilateral common carotid arteries. Normal saline was administered intravenously instead of PCr into rats of I/R group. After reporfusion for 48 hours, the rats were sacrificed and brains removed for detections of neuron apoptosis by using TUNEL, malondialdebyde (MDA) level by using chromtometry and calmodulin (CaM) activity by using ELISA. Results Compared with sham operation group, TUNEL-positive cells, MDA level and CaM activity increased in I/R group and PGr treatment group ( P ＜0.01). Compared with I/R group, TUNEL-positive cells, MDA level and CaM activity were lower significantly in PCr treatment group ( P ＜ 0.01). Conclusions PCr can lessen cerebral ischemic reperfusion injury and neuron apoptosis, the mechanism maybe relates to the attenuation of abnormalities in calcium balance and reduction of oxygen free radicals by PCr.