The bulging of the incision after thyroid surgery may be caused by the accumulation of fluid or blood under the incision, incision infection or scarring. In the early stage of post-thyroid surgery, bulging incision may be due to accumulation of fluid or blood under the incision, which may not have obvious discomfort, or may be manifested as localized swelling and pain, which can be clarified by local ultrasound examination. If the incision bulge occurs about 3~7 days after the operation, accompanied by redness and swelling at the incision, increased skin temperature and pain, it may be caused by incision infection. If the bulging occurs more than one month after surgery, it may be due to scarring of the incision tissue. If there is unexplained bulging of the incision, it is recommended that a local ultrasound or other examination be performed to determine whether there is any subincisional abnormality. If there is fluid accumulation, the incision can be opened to drain out the fluid, blood or pus under the incision and then change the medication in order to achieve the goal of healing.