Abstract：To investigation the effect of recombinant human erythropoietin preconditioning on the injury of astrocytes and the expression of MMP-9 after hypoxia, cerebral cortical astrocytes, newborn SD rat within 2 days were collected with the pure culture and the astrocytes were divided into control group, hypoxia group and rhEPO preconditioning group. The survival rate of astrocytes of 12h, 24h and 36h were determined by MTT assay. Inverted microscope and transmission electron microscope were used to observe the cell changes. The expression of MMP-9 mRNA and protein of astrocytes were detected by immunofluorescence and RT-PCR. It is shown that the astrocytes were swelled after hypoxia cultured 12h, with the maximal cell swelling observed at 36h. The rhEPO preconditioning can reduce the cell swelling remarkably. Ultrastructural alterations of astrocytes such as mitochondrial swelling after hypoxia can also be alleviated remarkably by rhEPO preconditioning. The results of MTT assay show that the survival rate of rhEPO preconditioning group were obviously higher than that of the hypoxia group(P<0.05). RT-PCR and immunocytochemistry analysis confirm that the expression of MMP-9 mRNA and protein was remarkably increased at 12h, peaked at 24h and declined at 36h after hypoxia cultured. Compared with hypoxia group, the expression of MMP-9 mRNA and protein in the rhEPO preconditioning group was significantly lower at 12h, 24h and 36h(P<0.05). The results show that rhEPO can improve the survival rate of astrocytes under hypoxia by inhibition of MMP-9.