Sudden nosebleeds in men in their 30s may be caused by dry rhinitis, nasal capillary hemangioma and acute leukemia. 1. Dry rhinitis: this disease often has symptoms such as nasal dryness, nasal itching, nasal congestion and nosebleed. Nasal cavity inspection can be seen mucous membrane slightly pale, dry, viscous secretion or thin crust attached to the front of the nasal cavity, and the mucous membrane of the anterior nasal septum appeared erosion, superficial ulceration. This is a common cause of sudden nasal bleeding in men in their 30s. 2. Nasal capillary hemangioma: this disease is common in 30 to 50 years old, more men than women, mostly occurring in the anterior part of the nasal septum, the anterior end of the inferior turbinate, the external nasal skin, etc., the volume is small, the diameter of most of the below 1.5cm, often for the polyp-like with the tip of the polyp, the surface is smooth or the formation of ulcers, easy to bleed. It may lead to sudden nosebleeds in men in their 30s. 3. Acute leukemia: leukemia is a malignant tumor of the blood system. At the onset, abnormal primitive cells and naïve cells (leukemia cells) in the bone marrow proliferate in large numbers and inhibit normal hematopoiesis, which can widely infiltrate various organs such as liver, spleen and lymph nodes. Manifested as anemia, bleeding, infection and infiltration and other signs, there may be a sudden nosebleed in men in their 30s. Men in their 30s with symptoms of sudden nosebleeds should seek medical attention in a timely manner to standardize treatment after a clear diagnosis.