Abstract: Subclinical hypothyroidism is a common endocrine disease during pregnancy. It may increase the risk of adverse pregnancy outcome and dysplasia of the offspring. However,It is still controversial whether the diagnosis of subclinical hypothyroidism during pregnancy should be treated with levothyroxine. Moreover,what kind of circumstances need to start drug treatment,how to adjust the drug dose,there is still disagreement. Therefore,more scientific and rigorous and large sample of research results are needed to clinical practice and accurate treatment of subclinical hypothyroidism with levothyroxine.