To study the effect of hypothyroidism of pregnant women during pregnancy on the intelligence and development in middle and long term of their offspring. Methods: The offsprings of 80 women with hypothyroidism during pregnancy from January 2017 to June 2019 were selected as subjects．According to the effect of thyroid hormone replacement therapy of the women, their offspring were divided into group A (31 cases with their mothers had good hypothyroidism control) and group B (49 cases with their mothers had poor hypothyroidism control)，another 40 offspring of normal pregnant women were selected in group C. The thyroid function, intelligence, and development of the offsprings in the three groups were recorded. Results：The levels of serum FT3 (4.79±0.75 pmol/L) and FT4 (17.63±2.68 pmol/L) of the offspring in group B were significant lower than those of the offsprings in the other two groups, but the TSH level (5.29±1.57 mIU/L) of the offsprings in group B was significant higher than that of the offspring in the other two groups (P<0.05). The great motor quotient (GMQ) and language quotient (LQ) of the offsprings in group B during the neonatal period, and 1, 2, and 3 years old years had decreased significantly, the personal social developmental quotient of the offsprings in group B during 2 and 3 years old years had decreased significantly, FMQ of the offsprings in group B during 1, 2, and 3 years old years had decreased significantly, and the length and weight of the offspring in group B during the neonatal period, and 1, 2, and 3 years old years were significant less than those of the offsprings in the other two groups (all P<0.05). Conclusion: After hypothyroidism of women during pregnancy is effectively controlled, the thyroid function, intelligence and physical development of their offspring have no significant different from those of the offspring of healthy pregnant women, but the offspring of women with continue hypothyroidism during whole pregnancy may show short-term thyroid dysfunction and backward of intelligence and physical development.