Baby drooling is generally more common between 3-4 months of age and 1-1.5 years of age, drooling at 3-4 months of age is because the salivary glands begin to develop vigorously at this age, while the swallowing function is not yet coordinated, which produces and swallowing disproportionate to the phenomenon so that the drooling increases. And 1-1.5 years old when the motor function is gradually perfect, but stability, precision and coordination is still poor, when the need to do fine movements when the whole body in order to control the accuracy of the mouth to compensate for the action, thus appearing the phenomenon of drooling, this kind of baby’s intellectual development is normal. If the baby is in a long-term open mouth and tongue and accompanied by special facial features and mental retardation, we should pay attention to the possibility of genetic metabolic diseases and chromosomal disorders, and need to go to the hospital in time to consult the doctor.