Recent studies indicate the involvement of glycosylation in the pathogenesis of Alzheimer′s disease (AD). α2,6-Sialylation, catalyzed by α2,6-sialyltransferase-I (ST6Gal-I), corresponds to the development of the infant brain and nervous system, however the mechanism of aberrant α2,6-sialylation affects multiple physiol. and pathol. conditions remains unclear.The present study, in vitro and in vivo, showed that expression of ST6Gal-I and α2,6-sialylation levels were up-regulated in cerebrospinal fluid and sera of AD patients.In addition, levels of α2,6-sialylation were also increased in brain and sera of AD model mice.Furthermore, deletion of ST6Gal-I reduced β-site amyloid precursor protein cleaving enzyme 1 (BACE1) levels and alleviated the impairment of learning and memory induced by scopolamine in rats.BACE1, a hyper-sialylated protein, plays a critical role in amyloid-β42 (Aβ42) productionST6Gal-I knockdown in Neuro-2a neuroblastoma cells (ST6Gal-I-KD-N2a) reduced the expression of BACE1 via promoting its ubiquitination.Deletion of ST6Gal-I suppressed amyloid precursor protein (APP) cleaved by BACE1, followed by a decrease in Aβ42 production, while alleviated Aβ42-induced apoptosis.This study first reveals a significant role of α2,6-sialylation in development and progression of AD, suggesting that ST6Gal-I is a novel glycan therapeutic target for AD diagnosis and treatment.