Objectives To investigate the outcome after thyroid hormone replacement therapy of preschool children with congenital hypothyroidism and its influencing factors,to evaluate the prognosis,treatment correctly,and provide the basis for the exploration of more perfect follow-up program. Methods Since 2007,cases were selected for screening and diagnosed in Maternal and Child Health Care Hospital that CH children after thyroid hormone replacement therapy for 2~3 years then were stopped,and continued to follow up more than one year.According to the thyroid function after discontinuation,they were divided into three groups:CH group,high TSH group and normal group.Intelligent,height,initial FT4 value and thyroid tissue of three groups were analysed at the same time. Results The intelligence and height development of children in three groups had no significant differences.The initial FT4 value had significant difference in three groups of children (F=3.65,P=0.032).The thyroid tissue abnormalities had significant difference in three groups of children(χ²=25.093,P=0,000). Conclusion Initial FT4 value and thyroid tissue abnormalities in children with CH have effects on prognosis;Follow-up of high TSH after treatment should be strengthened.