Urokinase acts directly on the endogenous fibrinolytic system, which can catalyze the cleavage of fibrinogen to fibrinolytic enzyme, playing the role of thrombolysis and prevention of thrombosis. The pharmacological effect of urokinase is to act directly on the endogenous fibrinolytic system, catalytic cleavage of fibrinogen into fibrinolytic enzyme, fibrinolytic enzyme can degrade fibrin clot, degradation of fibrinogen, coagulation factor V and coagulation factor VIII, etc., in the blood circulation, to play the role of thrombolytic; also can improve the activity of vascular ADPase, inhibition of platelet aggregation, to prevent the formation of blood clots. Urokinase is mainly applied to thrombolytic treatment of thromboembolic diseases, including acute widespread pulmonary embolism, coronary embolism and myocardial infarction within 6-12 hours, acute phase cerebrovascular embolism within 3-6 hours, retinal artery embolism, etc. It is also used for preventing thrombosis after prosthetic heart valve surgery, keeping vascular cannulae and drainage tubes of the thoracic cavity and pericardial cavity open. Urokinase common adverse reactions include bleeding, allergic reactions, nausea, vomiting, etc. It is contraindicated in patients with acute visceral hemorrhage, acute intracranial hemorrhage, old cerebral infarction, intracranial or intraspinal surgery within two months, intracranial tumors, arteriovenous malformations or aneurysms, hemorrhagic qualities, and severe difficult-to-control hypertension. As well as extended cardiopulmonary resuscitation, severe hypertension and other relative contraindications. Urokinase is mainly used for thrombolysis and prevention of thrombosis, it is recommended to follow the doctor’s instructions and active treatment to avoid delay.