Iodine 131 (131I) is an important means of treating differentiated thyroid cancer (DTC), and with the gradual increase in the incidence of DTC, the concept of 131I treatment of this disease is constantly updated. Clinical weight, the diagnosis and treatment of DTC, you may need to pay attention to these 34 points: 1, the evaluation of thyroid nodules is the main point of good and malignant differentiation. 2, emphasis on the evaluation of thyroid nodules with a family history of thyroid cancer, history of neck irradiation, age, gender and other malignant characteristics associated with thyroid nodules. 3, Serum thyroid stimulating hormone (TSH) levels should be routinely tested in patients with thyroid nodules. 4. Serum triglyceride (Tg) is not recommended to assess the benign or malignant nature of thyroid nodules. 5, Thyroid nodules with diameter >25px with higher than normal serum TSH should undergo thyroid 131I or 99Tc nuclear imaging to determine whether the nodule has an autonomic uptake function. 6, CT, MRI and 18F-FDGPET examination are not recommended as routine methods for assessing the benign or malignant nature of thyroid nodules. 7.Fine needle aspiration biopsy (FNAB) has the highest sensitivity and specificity when evaluating the benignity or malignancy of thyroid nodules preoperatively. 8, Ultrasound-guided FNAB can improve the success rate of sampling and diagnostic accuracy. 9, All DTC patients should be subjected to postoperative AJCCTNM staging and low, intermediate, and high-risk stratification of recurrence risk to help predict patient prognosis and guide individualized postoperative treatment and follow-up programs. 10.After DTC surgery, selective application of 131I nail clearance therapy. 11, pregnancy, lactation, planned short-term (6 months) pregnancy is prohibited 131I methylation therapy. Before 131I treatment, stop using levothyroxine (L-T4) for at least 2 weeks or use thTSH to raise serum TSH to >30mU/L. 13, 131I treatment should be low iodine diet (<50ug/d), avoiding the application of iodine-containing contrast medium and medications (such as amiodarone, etc.). 14. Patients should be instructed on radiation safety protection before 131I nail clearance treatment. 15.The 131I dose for nail clearing treatment in non-high-risk DTC patients is 1,11~3,7GBq. 16.Diagnostic nuclide scanning (Rx-WBS) examination after 131I nail clearing treatment should be carried out within 2~10 days after 131I nail clearing treatment. 17, Thyroxine therapy should be started within 24-72h after 131I nail-clearing therapy in DTC patients who have stopped thyroxine before treatment. 18, For iodine uptake DTC metastasis or recurrent lesions, 131I clearing treatment can be applied selectively. 19, For cervical lymph node metastasis, 131I 3,7~5,55GBq is given. 20, 131I is an effective treatment for DTC lung metastasis, and the commonly used dosage of 131I for treating DTC lung metastasis is 5,55~7,4GBq. 21, Isolated and symptomatic bone metastases should be considered for surgical resection. 22, Although 131I is difficult to cure bone metastases, it can improve the quality of survival of patients, so 131I treatment is appropriate for iodine uptake of bone metastatic lesions. 23.Regardless of whether the central nervous system metastases are iodine uptake or not, surgical treatment should be considered first. 24, DTC patients should be treated with TSH inhibition after 131I therapy. 25, 131I treatment according to the patient's risk stratification in a timely manner to give the appropriate TSH inhibition therapy, intermediate and high-risk DTC patients TSH inhibition to <0, 1mU / L, low-risk DTC patients TSH inhibition at 0, 1 ~ 0, 5mU / L. 26, L-T4 starting dose depending on the patient's age and concomitant diseases vary. 27, L-T4 should be taken early in the morning on an empty stomach. During the dose adjustment period, serum TSH should be measured approximately every 4 weeks. 28, The dose of L-T4 should be increased appropriately during pregnancy according to the increase in gestational weeks, and thyroid hormone and TSH levels should be tested regularly to adjust the dose of L-T4. 29.Pregnant patients with DTC who have received 131I therapy should maintain a TSH suppression level corresponding to their condition. 30, Suppressive therapy should be used to prevent and treat the corresponding complications. 31.Female DTC patients should avoid pregnancy for 6 to 12 months after 131I treatment. Contraception within 6 months for males. 32.Establish a 131I treatment isolation area in accordance with radiation safety and medical safety to ensure radiation safety of patients and the surrounding environment. 33, Routine use of MRI and 18F-FDCPET examination in DTC follow-up is not recommended. 34, In progressive iodine-refractory DTC that is ineffective with conventional treatment, treatment with targeted drugs such as sorafenib can be considered.