Sudden secretion of a large amount of saliva in the middle of the night may be caused by incorrect sleeping posture, abnormal secretion of salivary glands, oral environment, cerebrovascular disease and other reasons. 1. Incorrect sleeping posture: due to incorrect sleeping posture, such as sleeping in side or prone position, coupled with open mouth breathing, there may be a large amount of saliva secretion during sleep in the middle of the night, resulting in the phenomenon of drooling. 2. Abnormal secretion of salivary glands: when abnormal nerve regulation occurs, it will easily lead to gastrointestinal dysfunction, causing excessive secretion of salivary glands and abnormal secretion of salivary glands, resulting in sudden secretion of a large amount of saliva in the middle of the night. 3. Oral environment: If there are food residues in the oral memory, it will be easy to breed bacteria or oral mucosal disease, periodontal disease, etc., which may produce stimulation, leading to increased secretion of salivary glands, and sudden secretion of a large amount of saliva in the middle of the night. 4. Cerebrovascular disease: when the patient suffers from cerebrovascular disease, such as stroke, neurological dysfunction, there may be drooling, in the night time when the onset of the phenomenon, may also appear in the middle of the night sudden secretion of a large amount of saliva. If you often suddenly secrete a lot of saliva in the middle of the night, you should go to the hospital in time, under the guidance of a professional doctor to choose a targeted treatment method according to the condition.