Abstract: Objective To study the characteristics and clinical significance of electrocardiogram(ECG) for pregnant women with hyperthyroidism. Methods Seventy-nine pregnant women with hyperthyroidism were divided into normal ECG group and abnormal ECG group. Difference in complications of mothers and infants were compared between the two groups. Results Of the 79 pregnant women, 53(67.1%) had abnormal ECG. The incidence of pregnant hypertension, heart disease, premature delivery, fetal distress, low birth weight infant was significantly higher in abnormal ECG group than in normal ECG group(P< 0.01 or P< 0.05), However, no significant difference was observed in thyroid dysfunction of newborns between the two groups(P> 0.05). Conclusion Monitoring ECG is of great importance for observing the condition of pregnant women with hyperthyroidism and judging their clinical outcome.