Objective To investigate the protective effect of metformin treatment on cerebral ischemia in mice and its mechanism. Methods Thirty C57/BL6 mice were divided into control group and metformin group. Cerebral ischemia was modeled by MCAO surgery. 1-7 days after the surgery， mice in the metformin group were given metformin treatment at 50mg/kg intraperitoneally， while those in the control group were given the same amount of normal saline. On the 1st， 3rd， 5th and 7th day after surgery， the neurological function was assessed by Neurological severity scores （NSS） scale， and the residence time of mice on the rotating rod after cerebral ischemia was measured by Rotarod. On the 7th day after surgery， the expression levels of AMPK， pAMPK， HIF-1α， BCL-2 and ALK1 in the penumbra region of the two groups were detected by Western blot. On the 7th day after the operation， hemidark zone angiogenesis in the two groups of mice was detected by immunohistochemical staining. Results After treatment with metformin （50 mg/kg） after cerebral ischemia， the volume of infarction caused by metformin was significantly lower than that of the control group ［（14.2±2.23）% vs （37.8±1.77）%］. After administration of metformin， the number of blood vessels increased significantly compared with the control group ［（103.6±1.66） vs （57.7±1.01）］. On the 7th day， the NSS of mice in metformin group was significantly lower than that of control group ［（5.85±1.23） vs （3.33±0.57）］. There was no significant difference at other time points. The pAMPK/AMPK ratio in the metformin group was （1.79±0.24）， and the control group was normalized to （1.00±0.33）. The expression level of ALK1 was （2.01±0.52） in the control group， and （3.09±0.64） in the metformin group. Metformin could significantly increase the expression of BCL-2 ［（1.06±0.25） vs （0.53±0.07）］ and decrease the expression of HIF-1 α ［（0.71±0.12） vs （2.24±0.69）］. After the end of the 7th day of administration， the stay time of mice in the metformin group on the rod was significantly increased compared with that in the control group （all P ＜ 0.05）. Conclusions Metformin can reduce the volume of cerebral infarction， improve neurological symptoms and motor function， and promote vascular regeneration， which may relate to the increase of AMPK phosphorylation and ALK1 expression