To evaluate safety and therapeutic efficacy of sodium glycididazole (CMNa) combined with ,131,I radiotherapy for differentiated thyroid carcinoma (DTC), the 60 patients of DTC therapeutic protocols were selected and divided into 3 groups of the DTC 4.44 GBq ,131,I, DTC 3.70 GBq ,131,I, and combination of DTC 3.70 GBq ,131,I with CMNa, and the 20 patients of Graves' Disease were selected as the control group. Peripheral blood was sampled at,131,I pre-treatment of 1 day, and ,131,I post-treatment of 7, 91, and 182 days, thus analyzing lymphocyte micronucleus scores and karyotyping profiles. Compared with the control group, the lymphocyte micronucleus and chromosome mutation rates in ,131,I treated DTC increased after post-treatment of 7 days, recovered after post-treatment of 91 days, and did not bounce after post-treatment of 182 days. The micronucleus and chromosome mutation rates in the combination of DTC 3.70 GBq ,131,I with CMNa showed less significant variation than other treated DTC groups. Our results demonstrate that micronucleus assay and karyotyping analysis are favorable to evaluate ,131,I radiotherapy for DTC. The combination of the CMNa with ,131,I radiotherapy was safe for DTC patients without affecting the long-term therapeutic outcomes.