Many patients with differentiated thyroid cancer do not know whether they should undergo iodine-131 treatment after surgery. On the one hand, they expect that the tumor will not progress any further, but on the other hand, they are afraid of ionizing radiation damage, so they are very torn. My opinion is that when the benefits outweigh the disadvantages, then Iodine-131 therapy should be chosen. The indications for postoperative iodine-131 treatment of thyroid cancer are attached for reference only. 1.All differentiated thyroid cancer (DIC) with postoperative iodine absorption rate greater than 1%, and or thyroid imaging with thyroid gland shadowing; 2.Recurrent foci or metastatic foci cannot be removed surgically after DIC surgery, and the foci can concentrate iodine 131 on iodine 131 imaging, and the general condition is good; 3.Serum TG level is elevated greater than or equal to 10ug/L in the postoperative review.