Unstable angina may be caused by coronary artery stenosis, spasm and thrombosis and other factors. 1. Coronary artery stenosis: the symptoms of coronary artery stenosis are related to the degree of stenosis, mild stenosis usually have no obvious clinical symptoms, moderate stenosis usually have chest tightness with a little activity, and severe stenosis have cyanosis, which leads to angina pectoris. 2. Spasm: spasm is also known as coronary artery spasm, coronary artery spasm is a pathophysiological state. Due to the spasm site, severity and side circulation of different clinical types, so the coronary artery spasm may lead to unstable angina. 3. Thrombosis: platelet aggregation, fibrinogen and fibrin fragments increase the main D-dimer, the formation of intracoronary thrombus, thus easily lead to unstable angina. If the patient’s body discomfort, should immediately go to the hospital for consultation, for the cause of the effective treatment.