Objective In order to select appropriate size of embolizing granules and to achieve complete embolization and good therapeutic effect, the diameters of thyroid arteries in Graves disease was measured. Methods Multiple slides of embolized thyroid tissues from superior pole, body and inferior pole of resected thyroid glands were made. After being embeded and stained, diameters of arteries in various parts of thyroid glands were measured with microscope calipers (Olympus). Results Average diameter capillary network of the thyroid body gland adjacent to superior, infreior artery was 0. 12-0. 25 mm, and the smallest one was 0. 04-0. 11 mm. The diameter of isthmus was 0. 130. 15 mm. The average diameter of superior and inferior artery was 2- 5. 5 mm and 3. 0- 3. 75 mm measured by using interventional angiography Conclusion According to the diameters of arteries which were measured, complete embolization and good therapeutic effect can be achieved.