Bleeding is a common phenomenon in trauma, and excessive bleeding can cause shock and threaten the life of patients. According to the different damage vessels, it can be divided into three kinds: arterial bleeding, venous bleeding and capillary bleeding: 1.Arterial bleeding caused by arterial vascular damage. It is manifested as bleeding in the form of jets, bright red blood, bleeding volume, often can be found bleeding points. 2, venous bleeding caused by venous vascular injury. It manifests as slow outflow of blood, dark red color, relatively small amount of bleeding, and the bleeding site can be found. 3.Capillary hemorrhage caused by smaller vascular injury. It is manifested as blood oozing out from the wound (or wound surface), with bright red blood color, and often no bleeding point can be found. The bleeding can often clot on its own into a blood crust. Depending on the site of bleeding, there are three types of bleeding: external bleeding, internal bleeding, and subcutaneous bleeding: (1) External bleeding Blood can be seen coming out of the wound. General bleeding due to trauma is external bleeding. When we resuscitate trauma patients, most of the bleeding that needs to be stopped in time is external bleeding. (2) Internal hemorrhage The blood that bleeds is stored in the abdominal cavity or tissues and cannot be observed directly. The bleeding site can only be determined through the clinical manifestation of the patient and various examination means. Some trauma patients have the manifestation of hemorrhagic shock, and should be highly alert to the presence of internal bleeding. (3) Subcutaneous bleeding Bleeding within the subcutaneous tissue. The hemorrhage is characterized by bruised skin scar, local tissue swelling, and localized tension blisters on the skin. The skin surface is intact and unbroken. In trauma patients, contusions of the tissues during the injury can cause subcutaneous hemorrhage, which generally does not require special treatment.