Protein glycosylation is the most complex and diverse form of post-translational modification in human body. Meanwhile, glycosylation of peptides and proteins emerges as a promising strategy to improve the pharmacokinetic profile of peptide- and protein-based therapeutics. Owing to the importance of protein glycosylation, rigorous evaluation of the relationship between the precise structure and biological function of glycoproteins has to be per-formed. Recently, chemical synthesis, chemoenzymatic synthesis and semisynthesis strategy have attracted extensive attentions towards the prepara-tion of structurally defined glycopeptides and glycoproteins; the obtained synthetic glycoforms thus enable the thorough investigation of specific effects of protein glycosylation. This review highlights the recent progress in the development of novel strategies, preparation of homogeneous glycoproteins and exploration of structure-activity relationships. On this basis, the challenges and prospects are discussed.