Whether the other side of the thyroid cancer will become cancerous after hemisection needs to be judged according to the patient’s condition, if the patient has no metastasis, the other side will not become cancerous, if it has already metastasized, the other side may become cancerous. It is suggested that patients should pay attention to their diet and exercise appropriately after the operation. If there is no metastasis on the removed side of thyroid cancer, the other side will not become cancerous and the prognosis is good. If metastasis occurs on the cut off side, the other side of the thyroid gland is likely to become cancerous. Therefore, after surgery for hemisection of thyroid cancer, iodine 131 treatment, chemotherapy (e.g., cisplatin, adriamycin, etc.), and other treatments are routinely needed in order to remove as many remaining cancer cells as possible. Patients with thyroid cancer should pay attention to observation after the surgery, and review on time to detect recurrence as early as possible and treat accordingly.