Abstract: Mice bearing pulmonary adenocarcinoma models are treated with 188ReCL58. The effect judged through body weight loss, tumor burden and metastatic involvement of the organs are compared among the multiple low dose RIT, single large dose RIT and controls after successful implantation of tumor. When the treatment is initiated the 5th day after implantation, the tumor suppression effects of treatment groups are significantly better than controls, better results are achieved in 188ReCL58 multiple low dose RIT. Telomerase activity of tumor cells are detected before and after RIT, the activity is significantly brought down by RIT, and multiple low dose RIT is more efficient than single large dose RIT. The results show that multiple low dose RIT is more efficient for inhibition of telomerase activity.