Abstract: Small interference RNA (siRNA) was radiolabeled by using the bifunctional chelator of NHS-MAG₃ and SnCl₂●2H₂O. After transfected into Hepatocarcinoma HepG2 cells, labeled and unlabeled hTERTtargeted siRNA had the similar inhibitory rate about 76.7% measured by western blotting method. In the biodistribution study, the radio-active accumulation was primarily found in the kidneys, and then in liver. The radioactivity of hTERT-targeted siRNA in tumor increased from (0.82 ± 0.16) %ID/g to (0.97 ± 0.15) %ID/g from 1 to 6 hours after the administration. The uptake ratio of tumor to blood and tumor to muscle were 2.62 ± 0.70 and 6.02 ± 0.52, respectively, significantly higher than that of the control group (P<0.05). These results indicated that ⁹⁹Tc^m radiolabeled hTERTtargeted siRNA allows for prospective future and potential application value in the noninvasive visualization of tumor telomerase in vivo.