Congenital long QT syndrome (LQTS) is the most common inherited arrhythmia, fatal arrhythmias are the main causes of sudden death, and often induced by the premature ventricular contractions (PVCs). Ablation of the triggering PVCs may eliminate the fatal arrhythmias and prevent the sudden death in patients with LQTS. We report a 19-year-old boy diagnosed with type 3 LQTS, frequent fatal arrhythmias induced by PVCs with the identical QRS morphology. Successful ablation of the triggering PVCs was done and a single-chamber implantable cardioverter defibrillator (ICD) was implanted. There was no fatal arrhythmia events recorded by ICD during 29-month follow-up. Catheter ablation was the effective method to eliminate the fatal arrhythmias through ablation of the triggering PVCs in the present LQT3 patient.