Objective：To study the metabolism of high density lipoprotein cholesterol (HDL-C) and apolipoprotein A-Ⅰ (ApoA-Ⅰ) in different thyroid function status during pregnancy. Methods:This study recruited thirty cases of euthyroid, with nineteen cases of subclinical hypothyroid and eight cases of subclinical hyperthyroid pregnancy. The concentrations of fasting serum HDL-C and ApoA-Ⅰ were detected and analyzed from 9-12, 14-17, 23-26, and 37-40 gestational weeks. Friedman repeated measures ANOVA on ranks was adopted to analyze the changes of serum HDL-C and ApoA-Ⅰ at different stages. General linear model (GLM) was adopted to analyze the differences of serum HDL-C and ApoA-Ⅰ in different thyroid function status during pregnancy.Results:There were no significant differences of maternal serum HDL-C among different stages (χ2=5.428，P=0.143, χ2=2.027，P=0.567, χ2=2.885，P=0.410). There were significant differences of serum ApoA-Ⅰ during euthyroid and subclinical hypothyroid pregnancies (χ2=46.343， P＜0.001, χ2=35.984， P＜0.001), and no significant difference during subclinical hyperthyroid pregnancy (χ2=6.750， P=0.080). There were significant differences of serum HDL-C and ApoA-Ⅰ between euthyroid and subclinical hyperthyroid pregnancies (P=0.025，P=0.027), and no significant differences between euthyroid and subclinical hypothyroid pregnancies (P=0.378，P=0.549). Conclusion:Subclinical hyperthyroidism affected the metabolism of maternal serum HDL-C and ApoA-Ⅰ, which could affect the fetal growth and development. Subclinical hypothyroidism (after treatment with drugs) had no obvious effect on the metabolism of maternal serum HDL-C and ApoA-Ⅰ.