The child was a female, 4 years old. She was admitted to the hospital with post-activity panic and shortness of breath for 3 years. On examination, a grade 3 continuous murmur was found in the third and fourth ribs of the left sternal margin. The HP-7500 ultrasound showed that the right atrium, left and right ventricle were slightly enlarged, the aorta had mild regurgitation, and the tricuspid valve had mild-moderate regurgitation; the short-axis view of the aorta showed that the left coronary artery was significantly dilated at the beginning, with an internal diameter of 8 mm. Ultrasound diagnosis: right atrial fistula of the left coronary artery. After admission, coronary angiography showed dilated left coronary artery with drainage opening into the right atrium. The diagnosis of left coronary artery right atrial fistula was clear, and the AGA No. 8 plug device was selected for successful occlusion. Discussion: Congenital coronary artery fistula is an abnormal passage between the coronary artery and the heart chambers or large vessels, and the fistula is often significantly dilated and twisted or aneurysm-like dilated. The immediate echocardiographic sign is significant dilatation of the affected coronary artery, more pronounced at the beginning, which may be confined to a tumor-like enlargement. The fistula is usually long and tortuous, and the use of color Doppler ultrasound is useful to visualize the coronary artery and the site of drainage. Spectral Doppler ultrasound can observe the flow status of coronary artery fistulas. Endothelial cells of embryonic myocardial tissue form a synaptic gap, and when it grows up, the synaptic gap forms the coronary system, and if the gap is abnormally present, a fistula is formed. The shunted flow depends on the location and size of the fistula, and prolonged shunting increases the burden on the heart, causing congestive heart failure and pulmonary hypertension, while coronary fistula shunts can also cause coronary artery “blood theft” and eventually myocardial infarction. Coronary artery fistulas rarely close spontaneously, tend to thicken with age, and lead to an enlarged heart, which is prone to complications of infective endocarditis and should be treated actively once diagnosed. Echocardiography is specific, easy and accurate, and can be the imaging test of choice for the diagnosis of coronary artery fistula.