Objective To observe the occurrence of hypothyroidism of women in early pregnancy and to explore the relationship between age and occurrence of hypothyroidism. Methods 5998 women in early pregnancy and 639 non-pregnant women were enrolled in this study. The serum TSH and FT4 levels were measured by chemiluminescent method and the occurrence of hypothyroidism of women in early pregnancy was calculated. And all these gravidas were divided into different groups by age, then the occurrence of hypothyroidism were analysis and compared among different groups. Results The occurrence of hypothyroidism of women in early pregnancy was significantly higher than that of non-pregnant women（P＜0.05）, and there was no statistical difference in the occurrence of hypothyroidism among different groups (P>0.05). Conclusion Thyroid function test has important clinical significance, and the age is not one of the risk factors for hypothyroidism of pregnancy.