Abstract: The rat model of perinatal cerebral hypoxia-ischemia was prepared by permanent ligation of right common carotid artery combined with a temporary systemic hypoxic (inhaling 8% O₂+92% N₂) at 37℃ in 7-day-old SD rats. The relationship between beta-endorphin and encephaledema was observed in the established models. The encephaledema was deteriorated after the injection of beta-endorphin into cerebellomedullary cistern, while it was alleviated by the injection of beta-endorphin antiserum. It is suggested that beta-endorphin might play a role in the formation of encephaledema induced by cerebral hypoxic-ischemic injury in neonatal rats and plethoric beta-endorphin will aggravate encephaledema.