〔Abstract〕 Objective To investigate the changes of histone 3 lysine 9(H3 K9), methylated transferase(SUV39 H1) and glial fibrin acidic protein(GFAP), an active marker of astrocytes, in focal cerebral ischemia reperfusion injury. Methods The left middle cerebral artery occlusion model(MCAO model) was established by Koizumi method in the C57 BL/6 mouse model. The expressions of SUV39 H1, H3 K9 and GFAP in the cerebral ischemia reperfusion mice cerebral ischemia 2 h reperfusion 24 h group(the experimental group), the sham operation group and the blank control group were observed by behavioral analysis, slice staining, qRT-PCR, correlation analysis and Western blot. Results 2,3,5-triphenyltetrazolium chloride(TTC) staining showed that the cerebral infarct size of the experimental group was significantly higher than those of the sham operation group and the blank control group. The experimental group had obvious cerebral edema. qRT-PCR and Western blot showed that the expressions of SUV39 H1, H3 K9 and GFAP in focal cerebral ischemia-reperfusion group were significantly higher than those in the sham operation group and blank control group(P<0.05). Conclusion Focal cerebral ischemia reperfusion injury can stimulate the expression of SUV39 H1 and H3 K9. Meanwhile, the expression of GFAP also increases significantly. These results suggest that astrocyte activation may play an important role in increasing SUV39 H1 and H3 K9 expression in brain tissue of mice with focal ischemia reperfusion injury.