Thrombolytic therapy cannot dissolve all the thrombus, but it can dissolve a certain amount of thrombus depending on the type of thrombus and the time of thrombolysis. Thrombolytic therapy can dissolve red thrombus but not white thrombus, but the time window for thrombolysis varies for different sites of thrombus. The time requirement of thrombolytic therapy is more strict, for example, the thrombus in the heart, brain and lower extremity should be dissolved within the specified time, and the earlier the better. Red thrombotic thrombolytic drugs are generally composed of fibrin drugs such as urokinase, streptokinase and earth kinase, which can only dissolve the fibrin component of the thrombus, while red thrombus is rich in fibrin, so thrombolytic drugs can only dissolve red thrombus.1. Heart: The thrombolytic time for myocardial infarction is generally within 6-12 hours. If more than 12 hours, the thrombolysis rate is very low; 2. Brain: for patients with brain infarction, the time for thrombolysis of brain tissue is generally within 4-5 hours; 3. Lower limbs: the best time for thrombolysis of lower limb embolism is within 12-24 hours, in which the thrombus of the lower limbs can be effectively dissolved. White thrombus white thrombus is mainly composed of platelets, thrombolytic drugs not only cannot dissolve, but also activate thrombin function after use, leading to aggravation of thrombus, which is commonly seen in patients with unstable angina. Thrombolytic therapy is a common treatment for stroke, but during the treatment process, we should pay attention to the patient’s condition, discontinue the thrombolytic drugs if there is a change in neurological function within 24 hours, do CT to check whether there is brain hemorrhage, and if there is brain hemorrhage, symptomatic treatment can be performed according to the results of the expert consultation.