WPW syndrome is also known as the classic preexcitation syndrome. It is a ventricular pre-excitation caused by atrioventricular bypass and is associated with tachyarrhythmia. The preexcitation syndrome is divided into two types, type A and type B, based on the pattern of QRS waves in the anterior chest leads on the ECG. type B is when the main wave of QRS waves is down in lead v1 and up in leads v5 and v6, in which preexcitation occurs in the anterior lateral wall of the right ventricle. The preexcitation syndrome presents with tachyarrhythmias, mainly including atrial fold tachycardia, atrial fibrillation, atrial flutter, and ventricular fibrillation, of which atrial fold tachycardia is the most common, accounting for about 80%. This is followed by atrial fibrillation and atrial flutter and ventricular fibrillation. Catheter ablation bypass can cure the preexcitation syndrome radically. Catheter ablation should be performed as soon as possible for tachycardia with frequent episodes of tachycardia or with atrial fibrillation or flutter.