Objective To investigate the correlation of ¹³¹I radiotherapy tolerance with mutations of Kirsten rat sarcoma viral oncogene (KRAS) and v-raf murine sarcoma viral oncogene homolog B (BRAF) genes in differentiated thyroid cancer (DTC).Methods The clinical data and pathological tissue samples of 219 patients with DTC who received total thyroidectomy and postoperative ¹³¹I radiotherapy in our hospital between March 2010 and June 2015 were collected retrospectively. Patients were divided into the tolerant group and the sensitive group according to their tolerance to ¹³¹I radiotherapy. KRAS and BRAF^V600E mutations of the pathological tissue samples were detected.Results The proportion of patients with age≥45 years, follicular thyroid carcinoma (FTC), distant metastasis and metastatic lesion ≥ 1 cm in the tolerant group was higher than that of the sensitive group (P<0.05). KRAS mutation had a high incidence in FTC, while BRAF^V600E mutation had a high incidence in papillary thyroid carcinoma (PTC). In addition, both KRAS and BRAF^V600E mutation were associated with the largest diameter of primary tumor, AJCC TNM stage, lymph node metastasis, extraglandular invasion, distant metastasis and the size of metastatic lesions (P<0.05). The incidence of KRAS and BRAF^V600E mutations in the tolerant group was higher than that in the sensitive group, with statistically significant differences (P<0.05). Age ≥ 45 years, the size of metastatic lesion ≥ 1 cm, KRAS or BRAF^V600E mutation were independent predictors of ¹³¹I radiotherapy tolerance in DTC patients (P<0.05). The 5-year survival rate was lower respectively in the tolerant group, KRAS mutation group, BRAF^V600E mutation group, subgroup with KRAS mutation in tolerant group and subgroup with BRAF^V600E mutation in tolerant group (P<0.05).Conclusion KRAS gene and BRAF^V600E gene mutation were independent risk factors for ¹³¹I radiotherapy tolerance in patients with DTC, and had important significance for the prognosis assessment of patients with DTC.