Abstract: When protein, nucleic acid, polypeptide and antibody labeled with ⁹⁹Tc^m, bifunctional chelating agents(BFCA)are commonly used in order to avoid damages by directly labeling. We choose two BFCA:NHS-MAG3 and HYNIC as representation. The synthesis of these two BFCA is clear and the meth-ods of conjugating and labeling are mature. Through BFCA we can gain high radiolabeling yield, radiochemi-cal purity and specific activity. The usage of BFCA can provide necessary condition for molecular imaging and extensively clinical foreground.