Thyroid fine needle aspiration cytology is the most accurate and cost-effective method of diagnosing thyroid nodules and is now the preferred method of screening for thyroid nodular disease in many countries. The results of thyroid fine needle aspiration cytology have a 90% compliance rate with surgical pathology, with only a 5% false positive rate and a 5% miss rate. The application of this technology has greatly improved the accuracy of nodule diagnosis, made it clearer which patients need surgery and which do not, reduced the number of thyroid nodule surgeries by 35% to 75%, and increased the detection rate of thyroid cancer during surgery by 2 to 3 times, making surgery more targeted and reducing the cost of dealing with thyroid nodules by 25%. It has greater practical significance for selecting treatment options and has been increasingly promoted. Fine needle aspiration cytology of the thyroid is simple, inexpensive, highly accurate, and has been shown not to increase tumor implantation or spread through the needle tract. The only drawback of fine-needle aspiration cytology is the difficulty in differential diagnosis of follicular nodules, follicular adenomas and follicular carcinomas, which should be combined with medical history and other relevant laboratory tests.