The present invention provides an α-selective glycosylation method. The α-selective glycosylation method includes performing a reaction of a donor having a saccharide structure and a formamide-containing compound to form a glycosyl imidate compound; and in one pot environment, performing an addition reaction of the glycosyl imidate compound and an acceptor having a hydroxyl group to form an α-glycoside with high α-selectivity. The α-selective glycosylation method is applicable to the large scale production and easy to recover the formamide-containing compound.