Bandage is one of the important first aid measures for wound site. Timely and correct dressing can achieve the purposes of compression and hemostasis, reducing infection, protecting wounds, relieving pain, and fixing dressings and splints. On the contrary, the wrong dressing will lead to increased bleeding, aggravated infection, new injuries, sequelae and other adverse consequences. When dressing a wound, you should know whether there is any internal injury. At the scene of trauma first aid, we can't just bandage the visible wound and ignore other internal injuries.