Abstract: As the most common nuclide used to treat thyroid cancer, ¹³¹I, with high energy gamma rays, contributes the largest dose to medical staff, caregivers, relatives and the public because of its large amount of dosage in nuclear medical practice. Some control measures are required to limit the correlative persons' dose by its external exposure when the patients are released from the hospitals. This review will summarize the release criteria from hospitals of ¹³¹I therapy thyroid cancer patients between different countries or organizations in different periods. The variety of the release criteria is discussed.