Currently, we have morphological and functional examinations of the thyroid gland. For the examination of thyroid morphology, it can be done with many modern examination devices. The doctor will prescribe different tests, and we often do not understand why this is done and not that. What are the different functions of the different tests? Thyroid ultrasonography Thyroid B-type ultrasonography has high resolution of soft tissues, far better than X-ray, CT or MRI, with good repeatability and non-invasive features, and its application in clinical practice is becoming more and more widespread. The current high-resolution thyroid ultrasound is highly sensitive and can distinguish lesions of 2mm; patients with punctate enhancement, unclear borders, irregular morphology, rich blood supply and metastatic lymph nodes in the neck should be highly suspected of malignant changes and need to be reviewed in hospital as soon as possible. It is the main basis for clinical differentiation between benign and malignant. Thyroid nuclear imaging is classified as “hot nodules” and “cold nodules” according to the function of thyroid gland to concentrate iodine and technetium. It is useful to understand the location, shape, size and function of the nodules. CT and MRI of the thyroid gland are also important for the localization of thyroid tumors, but they lack characteristic changes. They are not an ideal test for thyroid tumors because they are expensive and inconvenient, but they are helpful for surgeons to understand the relationship between the tumor and surrounding tissues before surgery. Thyroid needle aspiration cytology or histology Thyroid fine needle aspiration cytology is ideal for differentiating benign from malignant thyroid tumors and is also useful for diagnosing chronic thyroiditis, but not for follicular carcinoma. Since coarse needle histology is a histological examination, the diagnosis is more accurate and can diagnose follicular carcinoma of the thyroid, but it is invasive. Therefore, the use of aspiration or biopsy under ultrasound guidance makes sample sampling more accurate and reliable. Positron tomography (PET) PET examination is very effective and non-invasive for the diagnosis of thyroid malignancies; however, this examination requires certain equipment, is expensive and requires out-of-pocket expenses, and the positive detection rate for smaller tumors is not high.