Hemophilia does not directly affect a patient’s life expectancy, but untreated bleeding from trauma can cause hemorrhagic shock, which has the potential to be life-threatening. Hemophilia is caused by a deficiency of clotting factors due to genetic defects and other reasons, resulting in clotting dysfunction, which manifests as spontaneous bleeding or repeated bleeding after mild trauma. Repeated bleeding from joints and muscles can lead to deformities of muscles and joints. Deficiency of factor VIII is called hemophilia A. Deficiency of factor D is called hemophilia B. Hemophilia does not directly affect life expectancy, but should be treated promptly when traumatic bleeding occurs to avoid bleeding that can lead to hemorrhagic shock and even death. At present, there is no effective treatment for hemophilia, and substitution therapy is the mainstay, requiring supplementation with appropriate clotting factors. Patients with hemophilia should take care to protect themselves from traumatic bleeding and other conditions as much as possible.