• Age: 18\

⁃ 75 years old (including 18 and 75 years old);

• ECOG: 0-2 points;

• Expected survival of more than 3 months; Differentiated thyroid carcinoma undergoing total thyroidectomy or subtotal thyroidectomy and confirmed as locally recurrent or metastatic disease by imaging, serum tumor marker, biopsy pathology; at least one measurable lesion (diameter of the tumor ≥10 mm), and meets the requirements of RECIST 1.1.

• Hemoglobin ≥80g/L, neutrophil ≥1.5×109/L, platelet count ≥80×109/L, serum creatinine ≤1.5× upper limit of normal or creatinine clearance ≥60ml/min, Blood urea nitrogen ≤2.5× upper limit of normal (ULN); Total bilirubin ≤1.5×ULN; Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤2.5×ULN; If accompanied by liver metastasis, ALT and AST≤5×ULN albumin ≥25 g/L;

• Women of childbearing potential must have taken reliable contraceptive measures or undergone a pregnancy test (serum or urine) within 7 days prior to enrollment, with a negative result, and be willing to use appropriate contraceptive methods during the trial and for 1 year after the last dose of 131I (for women), or for 6 months after the last dose of 131I (for men);

• Participants voluntarily joined the study and signed informed consent, with good compliance and follow-up.