If the first surgery for thyroid cancer is incomplete or if nodules appear again in the thyroid tissue remaining after thyroid surgery and the nodules are large or suspected to be malignant, reoperation of the thyroid gland is required. For thyroid cancer that was not completely removed in the first surgery, the best time for re-operation is within 3 weeks of the first surgery or 3 months after the first surgery. This is because, within 3 weeks, the postoperative response of thyroid is still dominated by edematous response and the adhesions between tissues after surgery during this period are still dominated by loose adhesions. Therefore, during this period of surgery, the postoperative adhesions can generally be separated, and therefore, there is usually no damage to normal tissues. However, after 3 weeks postoperatively, with the increase of scar reaction, the original loose edematous adhesions will be replaced by dense fibrinous adhesions, especially from 3 weeks to 3 months postoperatively. On the one hand, dense fibrinous adhesions can make the normal laryngeal nerve and parathyroid gland adhere to any other tissues; on the other hand, they also make the laryngeal nerve and parathyroid gland indistinguishable from fibrinous tissues, so once fibrinous adhesions are formed, the chance of reoperation to damage the laryngeal nerve and parathyroid gland increases greatly, and the risk of reoperation also increases greatly. However, for experienced surgeons, they can usually determine the site of residual thyroid initially through some special tests, such as CT, so that they can have a preliminary estimate of the risk of reoperation. Secondly, an experienced surgeon should have a better understanding of the anatomical site variation of the recurrent laryngeal nerve and parathyroid glands due to postoperative adhesions, and therefore, the risk of reoperation can be relatively reduced.