Objective To explore the effects of electroacupuncture on synaptic plasticity and microglial polarization and detect the expression of miR-21 / signal transducer and activator of transcription 3 (STAT3) pathway in rats with cerebral ischemia. Methods The distal end of the external carotid artery was double-ligated with a thin wire for 60 minutes to establish a rat model of focal cerebral ischemia. The neurological deficit score was used to evaluate the model preparation. The successful model rats were divided into a model group, electroacupuncture group, and nimodipine group.The control group comprised rats treated by a sham operation. After 3 weeks of treatment, the cerebral infarction volume was measured by 2,3,5-triphenyltetrazolium chloride staining, the synapse ultrastructure was observed by electron microscopy and analyzed by morphometry, and the microglial polarization was assessed by immunofluorescence staining. Additionally, the level of miR-21 in the cerebral cortex of rats in each group was measured by real-time fluorescence quantitative polymerase chain reaction, and western blotting was used to detect the levels of Janus kinase 2 (JAK2), p-JAK2, STAT3, and p-STAT3 in the cerebral cortex of rats in each group. Results The neurological deficit score, cerebral infarction volume, number of M1 microglia, and levels of miR-21, p-STAT3, and p-JAK2 were significantly higher and the number of M2 microglia, numerical density of synapsis (N_v ), volume density of synapsis (V_v ), surface density of synapsis ( S_v ), postsynaptic density (PSD), synaptic curvature, and width of the synaptic cleft were significantly lower in the model group than in the control group (P< 0. 05). The neurological deficit score, cerebral infarction volume, number of M1 microglia, and levels of miR-21, p-STAT3, and p-JAK2 were significantly lower and the number of M2 microglia, N_v, V_v, S_v, PSD, synaptic curvature, and width of the synaptic cleft were significantly higher in the electroacupuncture group and nimodipine group than in the model group (P<0. 05). Conclusions Electroacupuncture can promote synaptic remodeling and induce microglial polarization from M1 to M2 in rats with focal cerebral ischemia.