A 19-month-old female was admitted to our hospital due to her distinctive facial features. She was diagnosed with Down syndrome based on a chromosomal examination. She was also diagnosed with a complete atrioventricular canal defect accompanied by a large atrial (1.08 cm) and ventricular (1.88 cm) septal defect by echocardiography. The blood flow velocity and pressure gradient at the level of the common valve were 4.2 m/s and 70 mm Hg, respectively. The child has had difficulty feeding recently. An elective surgical repair was planned to improve her heart function. In this case, the key points of anesthetic management include preoperative assessment of the possibility of airway obstruction and difficult intubation, intraoperative vigilance for the occurrence of conduction block, and the prevention and control of perioperative pulmonary hypertension crisis.