What is acute coronary syndrome? It is a group of clinical syndromes of acute or subacute myocardial ischemia caused by atherosclerotic plaque rupture, thrombosis or vasospasm of coronary arteries, including unstable angina, acute myocardial infarction and sudden ischemic death of the heart. Acute coronary syndrome accounts for about 30% of coronary heart disease, is a common clinical cardiovascular emergency, and is also an important cause of acute death. The clinical manifestations of acute coronary syndromes vary widely, and the severity of clinical events in the coronary arteries is related to the degree and location of plaque rupture, thrombosis, the time required for complete occlusion, and the surrounding blood flow. Acute coronary syndromes are divided into ST-segment elevation and non-ST-segment elevation according to the electrocardiographic manifestations, where non-ST-segment elevation is further divided into unstable angina and non-ST-segment elevation infarction, while ST-segment elevation mainly refers to acute myocardial infarction. The pathophysiological differences between the two may be that the non-ST-segment elevation type is pathophysiologically based on incomplete thrombus occlusion of arteries or microembolism, mainly white thrombus with platelet predominance, whereas the ST-segment elevation type has complete thrombus occlusion of arterial vessels, red thrombus with red cell predominance. The two differ in their clinical presentation and treatment strategies. In acute myocardial infarction with ST-segment elevation, urgent reperfusion of the infarcted artery must be performed with antithrombotic, thrombolytic and/or coronary intervention. Now we advocate the “green channel” to save myocardium and lives, to further improve the success rate of acute myocardial infarction, reduce the death rate and improve the quality of patients’ survival. Unstable angina and non-ST-segment elevation infarction are not suitable for thrombolytic therapy, and active antithrombotic, anticoagulant and anti-ischemic treatment and/or coronary intervention is advocated to prevent the condition from evolving into ST-segment elevation infarction.