A coronary artery fistula is a vascular anomaly in which the coronary artery opens directly into the heart or a large vessel via the fistula. It is a very rare disease, accounting 0.2〜0.4% of congenital heart disease. We experienced two cases of coronary artery fistula that could be diagnosed by fetal ultrasound. In case 1, abnormal blood flow in the atria by the color Doppler method and abnormal blood flow waveform by the pulse Doppler method were the triggers for the diagnosis. In case 2, abnormal luminal structure in B-mode and abnormal blood flow in the right atrium by color Doppler were the triggers for the diagnosis. Patients with a coronary artery fistula are at risk of developing pulmonary hypertension and congestive heart failure in the early postnatal period. In addition, there is a risk of myocardial ischemia in the vascular perfusion area where the coronary artery fistula exists. Therefore, prenatal diagnosis is important for a favorable outcome. The combined use of color Doppler and pulsed Doppler in fetal ultrasound is of great significance.