Heparin has anticoagulant effect both in vivo and in vitro, divided into subcutaneous injection and intravenous injection, peaking at 3h after subcutaneous injection and taking about 10-12h to metabolize. After intravenous injection, the half-life of heparin in vivo is 1-6h, and the effect will gradually disappear around 3-4h. Heparin is widely used clinically, mainly for thromboembolic diseases, myocardial infarction, and fetal preservation treatment. Heparin is not absorbed orally, but is well absorbed by subcutaneous, intramuscular or intravenous injection, and is distributed in blood cells and plasma after absorption, and part of it can be diffused to the extravascular tissue space. Usually, heparin gradually takes effect 20-60 min after subcutaneous injection and reaches its peak at about 3h, while it enters the half-life at 5h and can be metabolized at about 10-12h, which is mainly excreted through the kidney. Meanwhile, the half-life of heparin after intravenous injection is 1-6h, with an average of 1.5h, which is related to the dosage and individual physical condition. The maximum anticoagulant effect can be achieved immediately by direct intravenous injection, after which the effect gradually decreases and the coagulation time knot returns to normal after 3-4h. In addition, patients should be promptly reviewed during the treatment with heparin, and liver and kidney function review and D-dimer review should be performed.