Objective To investigate the role and underlying mechanism of atorvastatin on hyper-glycemia induced hemorrhagic transformation(HT)in a mouse model of cerebral ischemia.Meth-ods A total of 36 SPF-grade male C57BL/6 mice were randomly divided into sham operation group,HT model group and atorvastatin group,with 12 mice in each group.HE staining was used to observe cerebral hemorrhage,immunofluorescent staining was employed to detect the integrity of blood-brain barrier,and Western blotting was applied to measure the protein expression of IgG,ZO-1,occludin,claduin5,MMP-2 and-9 in ischemic penumbra brain tissues.Results Com-pared with sham operation group,the neurological deficit score,mortality rate,HT incidence,HT grading score,IgG fluorescence intensity,and protein levels of IgG,MMP-2 and-9 were signifi-cantly increased,while the protein levels of ZO-1,occludin and claudin5 were obviously decreased in the HT model group(P＜0.01).Atorvastatin treatment resulted in significantly lower neuro-logical deficit score(2.73±1.19 vs 3.91±0.94),mortality rate(16.7％vs 41.6％),HT incidence(58.3％vs 91.6％),HT grading score(1.00±1.04 vs 2.58±1.13),IgG fluorescence intensity(504.30±105.52 a.u vs 859.91±153.28 a.u),and protein levels of IgG(4.55±1.40 vs 12.06± 3.73),MMP-2(1.87±0.41 vs 2.95±0.68)and-9(1.47±0.24 vs 2.12±0.23)(P＜0.05,P＜0.01),and increased protein levels of ZO-1(1.55±0.20 vs 0.53±0.10),occludin(0.92±0.11 vs 0.35±0.07)and claudin5(0.58±0.04 vs 0.30±0.05)(P＜0.01)when compared with the HT model group.Conclusion Atorvastatin can reduce the permeability of blood-brain barrier by in-hibiting the activation of MMP-2 and MMP-9 and up-regulating the protein levels of ZO-1,occlu-din and claudin5,and thus attenuate hyperglycemia-induced HT.