Immunohistochemistry of the thyroid gland is a qualitative, localized, and relatively quantitative study of thyroid tumors using antigen-antibody reactions and chemical reactions to develop color. Immunohistochemistry of thyroid is a process of characterization, localization and relative quantification of thyroid tumors by using the basic principles of immunology, i.e., the principle of specific binding of antibodies to antigens, and then identifying the antigens in tissue cells by chemical reaction that causes the chromogen labeled with the antibody to develop color. Immunohistochemistry can be useful in the diagnosis and differential diagnosis of malignant tumors, in determining the site of origin of metastatic malignant tumors, and in the pathologic staging of a particular type of tumor. Patients who need to undergo thyroid immunohistochemistry should cooperate with their doctors so that they can make a more accurate judgment of the patient’s condition and formulate a more appropriate treatment plan.