Leech is a commonly used herbal medicine and also one of the most powerful herbal medicines with anticoagulant effect found so far. It has the effect of breaking blood stasis and expelling blood stasis, and can be used to treat conditions caused by qi stagnation and blood stasis. Common cerebral thrombosis, sequelae of cerebral hemorrhage, myocardial infarction, coronary heart disease, angina pectoris blockage and amenorrhea can all be treated with leeches. According to the clinical pharmacology, leech has the function of improving blood circulation and inhibiting platelet agglutination, which is widely used in the prevention and treatment of various cardiovascular and cerebrovascular diseases. In addition, leech also has certain anti-cancer effects, which can inhibit the growth and metastasis of cancer cells for liver cancer, bone cancer, kidney cancer, lung cancer, etc.