〔Abstract〕 Objective To investigate the change of astrocyte in different regions of immature hippocampus after hyperoxia. Methods In order to set up a model of neonatal hyperoxic immature brain injury, postnatal 6 d rats were taken into 80% oxygen for 24 h as hyperoxia group, and were taken into air room for 24 h as control group. All rats were sacrified for brain tissue at postnatal 7 d, 14 d, and 21 d. Fluorescence intensity of astrocyte in dendate gyrus, hilus and CA1 regions were tested by immunohistochemistry. Results Fluorescence intensity of astrocyte in hilus of hippocampus after 24 h 80% hyperoxia deceased significantly compared with control group at postnatal 21 d. Ratio of fluorescence intensity in cell proliferation and astrocyte in hilus and CA1 regions after hyperoxia deceased significantly compared with control group at postnatal 7 d. Conclusion 24 h 80% hyperoxia inhibited astrocyte growth and proliferation in immature hippocampus.