Abstract：Significant prolongation of QT interval would easily cause malignant arrhythmias, and therefore in the research and development of new drugs, great importance should be attached to the evaluation of QT interval prolongation. As a necessary guiding principle for new drug research and development, ICH-E14 Guidelines, in the form of industry norms, stipulates that new non-antiarrhythmic drugs must be evaluated for QT/QTc interval prolongation before marketing. It means that electrocardiogram (ECG) monitoring will play an important role in the safety evaluation of this kind of drugs. In order to complete the collection and comprehensive analysis of ECG data with high standards and quality, this paper focuses on the methodology of QT/QTc interval measurement from several aspects. It introduces the requirements for instruments and personnel during QT interval measurement, the selection of measurement leads, the determination of QT interval starting and end points, QT interval measurement under different circumstances，different correction methods for QT intervals, and notes during data measurement.
