Drool is medically known as saliva, a colorless, clear, frothy, slightly cloudy liquid. Drooling while sleeping is generally caused by the following reasons: improper sleeping posture, such as sleeping on the table, sleeping on the side, etc. are very easy to cause drooling. Poor oral hygiene, the temperature and humidity in the mouth is most suitable for the propagation of bacteria, food debris on the teeth and tooth surface, prone to periodontal disease. All of these undesirable factors stimulate, can cause drooling while sleeping. Malformation of the teeth, especially the convex type malformation of the teeth, the front teeth forward protruding more obvious, sleep lip is very difficult to completely cover, covered in the front teeth, the upper and lower lips are often naturally separated from each other, it is easy to often drooling. Disorders of neuromodulation, the regulation of salivary secretion is entirely neural reflexive. Neurosis, or other systemic diseases that may cause vegetative nerve disorders, will occur in the disorder of neuromodulation, which will cause the brain to send out wrong signals, causing an increase in salivary secretion.