【Objective】 To probe the expression of myelin-associated glycoprotein (MAG protein) at hippocampus dentate gyrus and cortex in hypoxic ischemic brain damaged (HIBD) newborn rats. 【Methods】 64 healthy 7 days old Sprague-Dawley rats were randomly divided into tow groups, the sham-operation and the HIBD mode group. The changes in expression strength of MAG protein at hippocampus dentate gyrus and cortex were observed by immunohistochemical method after hypoxic ischemia, HI 24 h, 48 h, 72 h, and 7 days. 【Results】 MAG protein was expressed both in hippocampus dentate gyrus and cortex. The mean optical density of MAG were different significantly between two groups at HI 24 h, 48 h, 72 h and 7days, P＜0.05, including P_24h< 0.01 in hippocampal dentate gyrus and P_24h< 0.001 in cortex. Either in the sham-operation or the HIBD mode group, the expression strength of MAG protein was varied in deferent pattern in hippocampus dentate gyrus and cortex 【Conclusions】 The expression strength of MAG protein is varied in different cerebral area. With aging, the expression strength of MAG protein is changed in unlike pattern. Therefore, in newborn rats which were injured with HI, the expression strength of MAG protein and the pattern are changed. It means that in certain time range,the changes in the expression of MAG protein reflects the neurons in some area are damaged by HI. Further more it could be concluded that the changes of MAG protein may play a role in early diagnosis of HIE in newborns.