In recent years, epidemiological studies have found that since China’s implementation of salt iodization, most residents’ iodine nutrition are in moderate or even excess state. Iodine excess and iodine deficiency can change the shape and function of the thyroid gland, which can lead to thyroid disease. Low iodine intake can cause endemic goiter, cretinism; and high intake of iodine can cause goiter, hyperthyroidism, hypothyroidism, autoimmune thyroiditis school, thyroid cancer, etc. At present, the iodine nutritional status in our country has changed, and the spectrum of thyroid disease has changed. Urinary iodine, as the main indicator of the level of iodine nutrition, is an important reference for the assessment of hazards and effects of prevention measures. Therefore, monitoring of urinary iodine levels and a correct understanding of the relationship between iodine intake and thyroid disease have practical significance on the prevention and treatment of thyroid diseases.