Glycosylation site mapping helps the identification of a glycosylation site, which can provide an indication of the function of that glycan. In addition, site-specific glycosylation analysis and assignment of a certain structure to a specific site can illuminate the protein’s glycosylation profile, microheterogeneity, and its activity. Glycosylation has great importance in the development of biological drugs because their glycan chains markedly affect product stability, activity, antigenicity, and pharmacodynamics. Glycosylation site mapping mainly contributes to glycan microheterogeneity.