Abstract:Thyroid diseases mainly include hyperthyroidism and hypothyroidism easily complicated by various types of arrhythmias. Atrial fibrillation and sinus tachycardia are commonly seen on the ECG of hyperthyroidism while sinus bradycardia and low voltage of QRS prevail on the ECG of hypothyroidism. In clinical practice, knowing of the ECG changes of thyroid diseases helps prevent and treat cardiovascular complications in the patients with thyroid diseases. It also helps in the clinical diagnosis and curative effect evaluation which contributes to accelerate the recovery of patients.