Drooling in sleep may be a harbinger of oral disease or cranial disease, and there are physiologic and pathologic factors. In infancy and early childhood, neural development is not sound, and the shallow base of the mouth will appear the phenomenon of drooling in sleep, which is a normal physiological factor. Pathologic factors include oral diseases, craniocerebral diseases and so on. Mouth ulcers or salivary glands function abnormally when the salivary glands produce too much saliva or there is inflammation of the salivary glands. There may also be craniocerebral diseases such as cerebral thrombosis, Alzheimer’s disease, etc., due to blood clots compressing the nerves, the phenomenon of drooling in sleep will occur. Sleep drooling needs to go to the stomatology department or neurology department in time for medical examination, to clarify the cause of the disease, and follow the doctor’s instructions to deal with it.