Objective To investigate the dynamic changes of mitofusin-2(Mfn2) expression in rat cerebral arteries after experimental subarachnoid hemorrhage (SAH) and to reveal the relationship between Mfn2 and cerebral vasospasm (CVS). Methods A SAH model was induced by endovascular perforation of the intracranial portion of the internal carotid artery. One hundred and forty six male SD rats were randomly divided into six groups: sham group and SAH groups which were sacrificed at different time points (24 hours, 48 hours, 72 hours, 7days and 14days). Mortality, neurobehavioral score and brain water content were measured. Histology was conducted to observe the morphological changes. Western blotting and RT-PCR were performed to measure the Mfn2 protein and mRNA changes of the major cerebral arteries at different time points after SAH. Results Blood clot surrounded the basilar artery gradually dissipated after SAH. HE staining showed that the most severe morphological vasospasm in basilar arteries was observed at the 24th hour after SAH. No positive immunohistochemical staining of Mfn2 was shown in the media layer of basilar artery at the 7th day after SAH. Western blotting showed that Mfn2 protein was remarkably increased at the 48th hour and the 72th hour after SAH compared to sham groups (P<0.05) and significantly decreased at the 7th day after SAH (P<0.05). The protein level at the 14th day after SAH was almost the same level with the sham and SAH 24 hours groups. The mRNA level changed in the same tendency as the protein level. Conclusion This study indicate that Mfn2 plays essential roles in both acute and delayed CVS which may provide a theoretical basis for understanding of the mechanism of the CVS after SAH.