Abstract: 　Objective　To explore the effect of different hypoxic duration on the brain white matter injury. Methods 　Newborn rats were randomly divided into two groups, normal group (n=24) and model group (n=45). The model group was divided into 3 subgroups (n=15) according to the time of hypoxia (50 min, 70 min, and 90 min). The animal model of white matter injury was established by unilateral carotid artery ligation in model group. After different duration of hypoxia, the mortality rate was recorded, the morphological changes of brain pathology was observed by hematoxylin eosin (HE) staining, myelin basic protein (MPB) of white matter was detected by immunofluorescence staining and motor function was evaluated by climbing slope test. Results　The mortality rates significantly increased with prolonged hypoxia. The mortality rate was as high as 60% in 90 min subgroup. The HE staining showed that there were no obvious injury in 50 min subgroup, selective white matter injury on the operative side appeared in 70 min subgroup, and a wide range of infarction of white matter, hippocampus, and cortex appeared in 90 min subgroup. MBP semi-quantitative scores of white matter injury were higher in 70 min subgroup (3.89 ± 0.47) and 90 min subgroup (4.72 ± 0.57) than that in the normal group (0.06 ± 0.24), the difference was statistically significant (P <0.05). In climbing slope test, the subgroups had different degrees of motor dysfunction on affected side with 90 min subgroup being the most serious. Conclusions　White matter injury model could be established by unilateral carotid artery ligation, and different hypoxic duration significantly affects the range and degree of injury.