Reperfusion injury is a condition in which an embolism occurs in a vital organ of the body, resulting in insufficient blood supply to the vital organs. When thrombolytic therapy is given or collateral circulation is established, the vital organs are resupplied with blood, but more serious damage occurs to these organs, and this condition is called reperfusion injury. In clinical practice, the common sites of reperfusion injury are reperfusion injury after myocardial infarction and reperfusion injury after cerebral thrombosis. The pathogenesis of reperfusion injury is not yet fully understood, but a large number of clinical studies have found that reperfusion injury is related to the large influx of Ca ions and the generation of a large number of free radicals after the blood supply is restored. This is because the large amount of free radicals produced can have a more pronounced toxic effect on nerve cells and cardiomyocytes, which are not damaged. In clinical practice, Ca ion antagonists can be used in order to prevent reperfusion injury, as well as the application of free radical scavenging drugs.