Prothrombinogen is present in plasma and is the predecessor substance of thrombin, also known as coagulation factor II. The normal value of prothrombin in plasma is about 10-15mg/dl, while the prothrombin time is about 12-14s, and its activity can reach 75%-100%. It reflects the function of peripheral blood coagulation, mainly the activity of coagulation factors I, II, V, VII and X in plasma, and is also a screening test for the presence or absence of disorders in the external coagulation system of the organism. If there is an abnormality of prothrombin, such as prolongation or shortening, it repeatedly suggests the presence of congenital abnormal disease or acquired secondary changes that cause prolonged disease. The main manifestations are congenital deficiencies of coagulation factors II, V, VII and X and fibrinogen deficiency, absence of fibrinogen or abnormal fibrinogenemia. In addition, severe acute and chronic liver disease, obstructive jaundice, and vitamin K deficiency can also lead to abnormal prolongation of prothrombin. Diseases causing prothrombin shortening are mainly based on congenital coagulation factor V hyperplasia, thrombophilia, and long-term oral contraceptive use.