Abstract: Four new N 2S 2 or N 3S small peptide chelators are synthesized based on renal function imaging agent 99Tc m-MAG 3 as fundamental structure by introducing natural amino acids according to reasonable structure-activity relationships. All the new compounds are identified on the basis of the spectroscopic data, such as IR, 1H NMR, 13C NMR, MS and elemental analysis. All the chelators are labeled with technetium-99m and further tested for the biological activity in mice. The biodistribution results in mice indicate that 99Tc m-MVGG has high kidney uptake, good retention, quick blood clearance and high activity ratios of kidney to other tissues, suggesting that it would be a new potential renal function imaging agent; 99Tc m-MPGG has better kidney accumulation and higher activity ratios of kidney to blood; 99Tc m-MVTC and 99Tc m-MPTC have higher heart accumulation.