Coagulation is the process by which human blood has a liquid state to a solid state. Coagulation is the amplification of a series of coagulation factors, culminating in the activation of fibrinogen into fibrin and the formation of a fibrin clot to stop bleeding. There are two coagulation pathways: 1. Endogenous coagulation pathway: The initiating factor of the endogenous coagulation pathway is the coagulation factor Ⅻ. When the vascular endothelium is damaged, coagulation factor III and coagulation factor Ⅻ are activated to initiate the endogenous coagulation pathway and the endogenous coagulation pathway, 2. Exogenous coagulation pathway. The initiating factor is tissue factor, which is coagulation factor III, and after a series of amplification of coagulation factors, the initiating factors of these two coagulation pathways are not the same, but ultimately both activate thrombin and then fibrinogen. After the activation of fibrinogen, fibrin clots are formed and together they complete the coagulation process.