Iodine deficiency disease (IDD) is an endemic disease that affects the quality of our nation, and salt iodization is a commonly used intervention measure at home and abroad. 1990 World Summit for Children put forward the goal of global elimination of IDD by 2000, and Premier Li Peng signed the commitment on behalf of our government. 1994 State Council approved and issued the “Outline of China’s 2000 Plan for the Elimination of Iodine Deficiency Disease”, and since 1994 Salt iodization has been implemented nationwide since 1994, and by 2000, China achieved the goal of eliminating iodine deficiency disorders, to which salt iodization is credited. With the implementation of salt iodization nationwide, an increase in the incidence of thyroid disease was gradually observed. In Europe, where salt iodization was introduced about 10 years earlier than in China, there was an increase in thyroid disorders 2-3 years after salt iodization, with a significant increase in the incidence of thyroid nodules, especially autonomous functional thyroid nodules. Later the incidence gradually stabilizes, and after 6-8 years the incidence of thyroid disease begins to fall back. The increase in thyroid incidence after salt iodization is considered by many experts to be due to salt iodization, as China’s coastal areas have a high iodine intake and are not traditional IDD disease areas. It is known from animal experiments that the current amount of salt iodization has not been able to replicate thyroid disease, and the increase of several times still did not show thyroid nodules in animals. Therefore, there is no sufficient evidence that salt iodization is responsible for the increase in thyroid disease. Coastal areas are not iodine deficient at present, what we should pay attention to is the problem of iodine excess, although there is no survey data and scientific research data as a basis, but the increase of iodine in thyroid disease is at least one of the important causes. Therefore, it is correct to develop the appropriate salt iodization concentration or choose whether to iodize salt according to the iodine nutrition status in different regions.