Abstract: Differentiated thyroid carcinoma is the most common malignant tumor of the endocrine system, with an increasing incidence rate in recent years. Patients with papillary thyroid carcinoma might have a high incidence of cervical lymph node metastasis. Ultrasound and ultrasound guided fine-needle aspiration cytology is a highly sensitive and specific process for detecting the cervical lymph node metastasis. And the accurate determination of the characteristics of cervical lymph nodes is critical to make the choice of reoperation, ¹³¹I radiotherapy and follow-up after ¹³¹I therapy as well.