ST segment changes on ECG are commonly seen in pathologic changes of the heart, such as primary or secondary cardiac lesions, which require treatment; they can also be seen in physiologic changes, which are related to poor mood and age, and do not require treatment. To determine heart disease, electrocardiogram is indispensable, in which ST segment changes are of great clinical significance. However, many factors can cause ST segment changes, and the diagnosis of the disease needs to be combined with the medical history, symptoms, signs, and other auxiliary examinations, and also pay attention to the dynamics of the ST segment changes. ST segment changes may be seen in the following pathologic diseases: unstable angina, acute myocardial infarction, myocarditis, pericarditis, electrolyte metabolism disorders, pulmonary infarction, aortic coarctation, cerebro-cardiac syndrome and so on. Most of these conditions are critical and require early medical attention. ST segment changes may also be related to physiological factors, such as long-term anxiety and depression, menopausal women, tachycardia, etc., may appear ST segment changes, these cases generally do not need special treatment, but be careful to identify with pathological diseases. ST-segment changes on ECG are mostly pathologic, and it is recommended to go to the cardiology department for consultation and treatment according to the doctor’s instructions.