Abstract The aim of this study was to see whether Sodium Glycididazole （CMNa） could enhance the in situ tumor efficacy of radiation, using 4 different tumor models bearing mice. The results showed that in comparison with the irradiated group alone, CMNa could decrease the velocity of tumor growth and increase the days of Tumor Growth Delay（TGD） evidently in all four tumor types. CMNa showed radiosensitizing activity for all tumors with SERs greater than 1.3. It demonstrates that the novel radiosensitizer can potentiate the in situ anti-tumor efficacy of radiation and has different radiosensitization effect among the tested tumors. Whether the new radiosensitizer CMNa has any effects on normal tissue such as radiosensitive bone marrow was tested. Survival of bone marrow stem cells(CFU-GM） due to radiation alone or in combination with the drug was assessed. Nevertheless it did not enhance the radiosensitizing effect on normal bone marrow and SER=1. The Therapeutic Gain Factor（TGF） defined as SER of tumor divided by SER of normal tissue bone marrow is greater than 1.3. Maybe CMNa will be an effective new type radiosensitive drug for clinical cancer therapy.