Abstract: With the further research of antisense imaging, N-hydroxysuccinimidyl S-acetylmercap to acetyltriglycline(S-acetyl-NHS-MAG_3) as a novel bifunctional chelator is interested by scientists and used widely. It is proved that the radiolabeled products by the NHS-MAG_3-labeling method show high labeling yield, high specific activities, high radiochemical purity and desi-rable stability in vitro and in vivo. The binding with plasma protein of the labeled products is low. In addition, NHS-MAG_3 will not affect the specificity of hybridization of the antisense oligonucleotides and can increase the accumulation of the labeled antisense oligonucleotides in the cells. The properties NHS-MAG_3 make it suitable for labeling antisense oligo-nucleotides and possible to be a potentially useful radiopharmaceuticals for diagnosis and therapy.