Three months baby spit up water can be caused by a variety of reasons, generally consider the normal physiological phenomenon, indigestion, drinking too much water and other reasons. 1. Normal physiological phenomenon: three-month-old baby salivary glands began to secrete, and swallowing function is not particularly perfect, can lead to saliva can not be swallowed to spit (saliva); may also be the baby wants to teething or itchy teeth caused by the general need for treatment, to keep the mouth clean. 2. Indigestion: children due to the age of the digestive function is not yet sound, parents feeding and care of improper can lead to the occurrence of indigestion, in addition to spitting water, but also may be accompanied by abdominal distension, vomiting, crying, loss of appetite and other manifestations. 3. Drinking too much water: Because the baby stomach is relatively small, if parents frequently feed water, feed too much water can lead to the baby vomit water, pediatrics should be fed on demand, breastfeeding is generally not fed water, so as not to cause gastrointestinal burden. Three-month-old babies spit up water, there may be other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.