Objective: To investigate the correlation between serum Homocysteine (Hcy) and Thyroid Peroxidase Antibody (TPO-Ab) and the changes of thyroid hormone levels in pregnant women with hypothyroidism. Methods 110 pregnant women with hypothyroidism admitted to our hospital from May 2021 to October 2024 were selected as the hypothyroidism group, and 105 healthy pregnant women (normal thyroid function) who underwent prenatal examination in our hospital were selected as the control group. According to the number of weeks of pregnancy, the observation group was divided into: 34 cases in the first trimester, 39 cases in the second trimester and 37 cases in the third trimester. The control group was divided into: 33 cases in the first trimester, 40 cases in the second trimester and 32 cases in the third trimester. Hcy, TPO-Ab and thyroid hormone levels were detected and compared between the two groups. The levels of Hcy, TPO-Ab and thyroid hormone in the two groups were analyzed and compared. The correlation between Hcy, TPO-Ab and thyroid hormone levels in hypothyroidism group was analyzed. Results Compared with the control group, the levels of Hcy, TPO-Ab and TSH in the hypothyroidism group were significantly decreased, and the level of FT3 was significantly increased (P<0.05). There was no significant difference in FT4, T3 and T4 levels between the two groups (P>0.05).There was no significant difference in the levels of Hcy, TPO-Ab, TSH, FT3, FT4, T3 and T4 in the control group during the first, second and third trimesters of pregnancy (P>0.05).The levels of Hcy, TPO-Ab and TSH in hypothyroidism group were compared:early pregnancymiddle pregnancy>late pregnancy, there was a significant difference (P<0.05).There was no significant difference in FT4, T3 and T4 levels in the first, second and third trimesters of pregnancy in the hypothyroidism group (P>0.05).According to Pearson correlation, Hcy and TPO-Ab were positively correlated with TSH and negatively correlated with FT3 (P<0.05),there was no correlation with FT4, T3 and T4 (P>0.05).Conclusion Patients with hypothyroidism during pregnancy have abnormal levels of Hcy and TPO-Ab, and there is a significant correlation between them and TSH and FT3 levels.