Nosebleed from the mouth is a very common clinical phenomenon for the following reasons: the first reason is that the patient has arterial bleeding in the nasal cavity, and the bleeding volume is very large in a short period of time, resulting in a part of the bleeding, which not only flows from the front nostril but also trickles out from the posterior nostril and enters the mouth through the nasopharynx, causing the patient to spit out blood from the inside of the mouth. The second reason, some patients have bleeding from the posterior end of the nasal cavity. The common bleeding sites are bleeding from the posterior fornix of the inferior nasal tract, or bleeding from the artery at the pterygoid fossa or the olfactory fissure. This type of bleeding is more posterior and causes a large amount of accumulated blood to flow directly into the nasopharynx and into the mouth due to gravity, causing the patient to vomit a large amount of blood from the mouth. The third reason is that in some patients, during the process of nosebleed, some of the blood enters the maxillary sinus and sinus, and as the patient changes position, the accumulated blood comes out of the sinus and enters the nasopharynx, causing the patient to vomit blood out of the mouth.