More than 50% of patients with heart failure die from sudden cardiac death as a result of malignant arrhythmia. T wave alternans (TWA) is a convenient, noninvasive, and inexpensive testing modality, with a higher sensitivity and specificity for sudden cardiac death. Its prediction value for malignant arrhythmia may even exceed electrophysiologic study. Generally, the algorithms of TWA can be divided into frequency-domain and time-domain methods, and the latter has a stronger anti-interference ability. So far, a unified measuring formula and diagnostic criteria about TWA measurements have been created. Large clinical studies in recent years strongly suggest that TWA can predict sudden cardiac death, which can be used as a guide for the implanting of implantable cardioverter-defibrillator. This article reviews the current literature on recording techniques and clinical implications of TWA.