China is one of the countries seriously threatened by iodine deficiency. statistics from the 1990s show that iodine-deficiency areas are distributed in 1807 counties; there are nearly 8 million endemic goiter patients and 187,000 patients with typical endemic cretinism. More seriously, it is estimated that there are millions of subcretinism patients. The overall intelligence level of the population in the disease area has shifted in the direction of low IQ, and the numerous mentally retarded children have brought irreparable losses to the quality of our population and the development of our economy and culture. Since the 1960s, China has implemented a prevention and treatment strategy based on the supply of iodized salt to moderate and severe disease areas, which has brought the rampant epidemic of iodine deficiency disease under control. However, before 1995, China did not supply iodized salt to areas with mild iodine deficiency, nor did it take any other intervention measures.