Abstract: Surface electrocardiogram (ECG), as a basic method of physiological examination,  is indispensable in daily clinical diagnosis and treatment, especially in that of heart disease. The diagnostic value of ECG and its simplicity and convenience make it an important basis for effective treatment of patients. Therefore, rapid and accurate diagnosis of ECG is of great significance in guiding clinical treatment correctly. However, the interpretation of ECG is far from being easy, especially when it comes to the complex standard parameters of ECG. It is particularly important to master them. This paper reviews  the normal indexes of ECG in different ages.

Key words: electrocardiography, diagnosis, reference standards