Background: The molecular mechanisms of vascular cognitive impairment (VCI) are diverse and still in puzzle. VCI could be attributed to chronic cerebral hypoperfusion (CCH). CCH may cause a cascade of reactions involved in ischemia and neuro-inflammation which plays important roles in the pathophysiology of VCI. High-mobility group box protein 1 (HMGB1) is a non-histone protein that serves as a damage-associated molecular signal leading to cascades of inflammation. Increased level of HMGB1 has been established in the acute phase of CCH. However, the role of HMGB1 at the chronic phase of CCH remains elucidated. Methods: We performed modified bilateral common carotid artery occlusion (BCCAO) in C57BL/6 mice to induce CCH. We examined the cerebral blood flow (CBF) reduction by laser doppler flowmetry, the protein expression of HMGB1 and its pro-inflammatory cytokines (TNF-a, IL-1b, and IL-6) by western blotting and immunohistochemistry. The brain pathology was assessed by 7T-animal MRI and amyloid-b accumulation was assessed by amyloid-PET scanning. We further evaluated the effect of HMGB1 suppression by injecting CRISPR/Cas9 knock-out plasmid intra-hippocampus bilaterally. Results: There were reduction of CBF up to 50% which persisted three months after CCH. The modified-BCCAO animals developed significant cognitive decline. The 7T-MRI image showed hippocampal atrophy, although the amyloid-PET showed no significant amyloid-beta accumulation. Increased protein levels of HMGB1, TNF-a and IL-1b were found three months after BCCAO. HMGB1 suppression by CRISPR/Cas9 knock-out plasmid restored the CBF, IL-1B, TNF-alpha, IL-6, and attenuated hippocampal atrophy and cognitive decline. Conclusion: HMGB1 plays a pivotal role in the pathophysiology of the animal model of CCH and it might be a candidate as therapeutic targets of VCI.