Thyroid cancer is the malignant tumor with the highest incidence in the endocrine system, and its incidence is characterized by a clear gender bias. The annual incidence rate is 3/100,000 in men worldwide, while it is 2-3 times higher in women. High risk factors: 1, ionizing radiation: its risk is related to the age of receiving radiation, and generally decreases with age. 2, iodine: thyroid is not only more prevalent in iodine-deficient areas, but also often occurs in coastal areas with high iodine. 3, gender and estrogen: women are significantly higher than men. Estrogen can affect the growth of thyroid gland, and its high level may also be one of the cancer-causing factors. 4.Family factor: It is more common in patients with medullary thyroid cancer. Screening means: 1. Ultrasound examination: Ultrasound can clarify the size and boundary of thyroid tumor, and also can initially determine the nature of the mass. Its benign and malignant rate is over 90%, which is an important routine examination means. 2.Biopsy: For resectable thyroid masses, generally no preoperative biopsy is required and surgical resection can be performed. If malignancy is suspected, a rapid intraoperative frozen pathological examination can be performed to clarify the nature. 3.CT: It can clearly show the extent of the lesion, especially the extent of intra-thoracic extension and its relationship with the adjacent blood vessels, which can provide a reliable basis for the formulation of treatment plan. 4.Tumor markers: Patients with medullary thyroid cancer often have abnormally elevated serum calcitonin level, which can be used as tumor markers for medullary thyroid cancer. In addition, serum carcinoembryonic antigen also has certain reference value. It is recommended that high-risk groups should be palpated by a clinical specialist once every six months to once a year, and ultrasonography should be performed at least once a year.