Disclosed are a method for preparing a biomaterial having selectively functionalized tyrosine, a biomaterial having selectively functionalized tyrosine, and a pharmaceutical composition containing same as an active ingredient. The method for preparing a biomaterial to which a compound represented by chemical formula 2 is coupled, of the present invention, allows the compound represented by chemical formula 2 to be selectively coupled, in a high yield in a biomaterial, to tyrosine, which is present on the surface of an aqueous solution such that the coupling thereof to amino acids other than tyrosine does not occur and, when only one tyrosine is present, heterogeneous mixtures are not present and the inherent activity of the biomaterial is maintained, and thus the compound can be effectively used as a pharmaceutical composition containing a biomaterial drug as an active ingredient. In addition, the method can selectively functionalize tyrosine, and thus can be effectively used for tyrosine functionalization in a biomaterial.