Coagulation means blood coagulation. Blood coagulation is the process by which blood changes from a flowing liquid to an immobile gel, and is an important part of physiologic hemostasis. Essentially it is the process by which soluble fibrinogen in plasma becomes insoluble fibrin. Literally, it just refers to a series of disorders caused by hypo- or hyperfunction of coagulation factors, but actual coagulation includes many more disorders. Coagulation abnormalities are disorders in which the process of stopping bleeding is abnormal, including bleeding caused by the corresponding hypofunction, i.e., hemorrhagic diseases, and thrombotic disorders caused by the corresponding hyperfunction. Both bleeding disorders and thrombotic disorders are related to the number and function of platelets, the function of coagulation factors, the function of blood vessels, anticoagulation and fibrinolysis. In case of bleeding and thrombosis, it is necessary to go to the hospital to test the corresponding blood vessels, coagulation and platelets to find out the specific cause of the abnormality and then treat according to the doctor’s instruction.