A young patient of 25 years old was recently admitted to our department and had syncope every time he woke up in the morning. He had an ambulatory ECG, cranial CT, EEG, carotid TCD, and so on, but no reason could be found. Later, after taking a detailed medical history, it turned out that every time this young man had syncope, it happened when he woke up to urinate, and he fainted in the bathroom after urinating, and slowly woke up again after a few minutes. We finally gave him the diagnosis of urinary syncope. Urinary syncope is the sudden fainting at the beginning of urination, during urination, or when leaving the toilet after urination, which lasts for 30 seconds to 15 minutes before waking up. It occurs mostly in healthy men between the ages of 20 and 30. The main cause of urinary syncope is caused by a sudden drop in blood pressure, which mostly occurs at midnight or when waking up from a nap to urinate upright. It usually returns to normal after a few hours of rest. There are two types of nerves that control the internal functions of the human body, one is called sympathetic nerve and the other is called parasympathetic nerve. Sympathetic excitement inhibits urination, while parasympathetic excitement promotes urination, so urination is manipulated by the parasympathetic nerves. In addition to the parasympathetic nerve, which governs urination, the parasympathetic nerve also causes a slowing of the heart rate, dilatation of the peripheral blood vessels and a drop in blood pressure. Therefore, when you get up suddenly after sleeping to urinate, the parasympathetic nerves become abnormally excited, so the heartbeat slows down, the peripheral blood vessels dilate and blood pressure drops, which can cause a temporary shortage of blood supply to the brain. In addition, suddenly get up, from the horizontal position of sleep to upright position, the brain will also appear temporary ischemia, so that the above two factors together will lead to the phenomenon of urinary syncope. Sometimes, when urinating too hard to hold the breath and force, it will also stimulate the parasympathetic nerves, which will also cause insufficient blood supply to the brain through nerve reflexes, and then fainting will occur. This often happens in young men who are impatient, get up in a hurry to urinate hard, and want to “get it done” in a moment, of course, fainting will occur. Sometimes this symptom can also occur after holding urine for a long time, or after drinking alcohol. If you know the reason for fainting after urination, there are ways to prevent it. Generally speaking, urinary syncope can be prevented by taking the following measures: for those who develop after drinking, abstain from alcohol; do not get up to urinate immediately after waking up, but stand next to the bed for a while when you get up to urinate; urinate more slowly and not too hard. Generally, urinary syncope has aura symptoms, such as dizziness, panic, weakness of the lower limbs, etc. If these aura appear, squat down or sleep flat, and you will get better in a while. Of course, there is no aura at all, if the patient has a history of recurrent episodes, you can take a squatting position to urinate, while urinating with a hand to grab a support; stand for a while after urination, no discomfort before walking; if there is dizziness, dizziness to immediately squat; in the bathroom to avoid placing some sharp or fragile objects, so as not to cause unpredictable in the event of syncope. Urinary syncope is also occasionally seen in elderly people, mostly when they get up after sleep to urinate, and it is easily triggered by cold weather or alcohol consumption, and is more likely to occur in patients suffering from tuberculosis, neurasthenia and physical weakness. Therefore, the elderly in particular should be more careful to prevent fractures and cranio-cerebral injuries caused by falls during episodes of illness.