Abstract: Midkine (MK) has multiple biological functions, and plays an important role in the diagnosis and treatment of tumor. Midkine is generally overexpressed in diverse malignant tumors, and enhances proliferation, migration and angiogenic activity of tumor cells. Recent studies have found that MK is closely related with thyroid cancer. Immunohistochemical studies showed that MK expression in thyroid cancer cells and tissues was significantly higher than that of normal thyroid. MK level of the needle aspiration eluant had a good diagnostic value for the differentiationbetween benign and malignant thyroid nodules. MK is cytokinesecreted in the blood; it could be used as a serological marker for the differentiation between benign and malignant thyroid nodules. MK could also beapplied for the prognosis of differentiated thyroid carcinoma treated by ¹³¹I (whether with or without metastases). In addition, in the case of thyroglobulin antibody positivity, MK could be surrogated as a viable serological marker for predicting thyroid cancer metastasis. The major limitation of MK is lowoncological specificity. In many cases, it is necessary to measure MK with other specific tumor markers. Future researches should focus on the mechanism of MK in the occurrence, development and therapeutic resistance of thyroid cancer. This review discusses the value of MK as a thyroid cancer marker.