Objective　To explore the cause of atrial fibrillation during the head-up tilt test（HUTT). Method　The data of a child with vasovagal syncope in whom atrial fibrillation was induced in HUTT was analyzed retrospectively, and the related literatures were reviewed. Result　A 7-year-old girl was admitted with a history of 2 episodes of loss of consciousness last year. Each episode lasted for 2 minutes. There were no unusual neurological findings, and the blood chemistry results were all normal. Electrocardiogram and echocardiography did not reveal any abnormalities. Electroencephalogram, CT scans of the brain were normal. During the HUTT, 40 minutes after the start of tilting, the child felt nausea and chest tightness with pale face, at that time her blood pressure and heart rate were 87/49 mmHg and 50 beats/min. During lying down, the girl’s ECG showed sinus arrest of 5.3 seconds followed with escape rhythm of atrioventricular junction, atrial premature, atrial fibrillation. After half a year's health education and autonomic nerve function training, there was no syncope or atrial fibrillation. Conclusion　Increased vagal tone may induce atrial fibrillation during the head-up tilt test.