Abstract: ~(99)Tc~m-MAG_3(mercaptoacetyltriglycine), a recently developed renal imaging agent as an alternative to ~(131)I-OIH(hippuran), has been in use in clinic. In the study of ~(99)Tc~m-labelled renal radiopharmaceuticals, an important direction is the investigation of the relationship between their structure and behavior in vivo through changing the structure of ligands, which combine with ~(99)Tc~m to form the ~(99)Tc~m-complexes. To reveal the reasons that lead to the differences between ~(99)Tc~m-MAG_2 (mercap toacetyl diglycine), a potential renal imaging agent synthesized lately in our laboratory, ~(99)Tc~m-MAG_3 as well as ~(99)Tc~m DADS (N,N'-bis (mercaptoacetamido) ethylene diamine), the structure of ~(99)Tc~mMAG_2 is comfirmed by determining the oxidation state of ~(99)Tc~m, apparent charge and stoichiometric composition of the complex. The results show that ~(99)Tc~m complexes with MAG_2 to form Tc (Ⅴ) ON_2SO, which is similar to ~(99)Tc~m-MAG_3 and ~(99)Tc~m-DADS, with stoichiometric composition 1: 1, and that the oxidation state of ~(99)Tc~m is five and carboxylate oxygen is the donor atom.