Leech is a traditional Chinese herbal medicine. Hirudin is a natural polypeptide extracted from leeches and fresh saliva，which has anticoagulant effects and is widely used clinically，but not all varieties of leeches contain hirudin in the body. This article reviews the anticoagulant active substance components contained in several common leeches and the extraction and purification methods of hirudin，aiming to provide reference and reference for in-depth research on the method of efficient and rapid extraction of hirudin.