Thyroid cancer is one of the malignant tumors with the fastest increasing incidence in recent years. With the advancement of medical technology, the level of diagnosis and treatment of thyroid cancer has advanced greatly. Ultrasound imaging is the most important method to diagnose thyroid cancer. The following 4 features of thyroid nodules are shown on ultrasonography: 1. Nodules with many small calcifications, especially fine sand-like calcifications, suggest malignancy; 2. Nodules with abnormal blood flow, especially those with extremely rich blood flow, suggest malignancy; 3. Nodules with hypoechoic, or very hypoechoic, and uneven echogenicity suggest malignancy; 4. Nodules with irregular, burr-like edges suggest malignancy. Those suspected of malignancy need to be reviewed regularly, usually once every 2-3 months, preferably not more than six months.