Abstract: Since the concept of "click" chemistry was introduced by Barry Sharpless in 1999，it has gained considerable attention and developed quickly. In this review，the definition and classification of "click" reaction have been introduced. Among the different types of "click"reaction ， the application of Cu（I）-catalyzed Huisgen 1，3-dipolar cycloaddition of azides and terminal alkynes（CuAAC）to form 1，2，3-triazoles is remarkable. Its applications in labeling of biomolecules were reviewed from four parts：labeling of peptides and proteins，DNA and RNA，lipid in living cells，and viral surfaces.

Key words: "click" chemistry, triazoles, peptide, protein, DNA, RNA, lipid in living cells, viral surfaces