It is important to know that all metabolic and thermoregulatory activities of the human body must have the participation of water to complete, water is an important component of the human body. One source of water is obtained from drinking water and food, which is the main source; the second is the tissue metabolism and food in the body oxidation process can also produce part of the water (100kca1 can produce about 12g of endogenous water). Children’s whole body water content more than adults, such as newborns whole body water content of about 78% of body weight, 65% at the age of 1 year, adults accounted for 60%-65% of body weight. A healthy infant consumes 10%-15% of body fluids daily, while adults are 2%-4%. The distribution of water in the body also varies by age. Children’s water needs are closely related to energy intake, food type, maturity of kidney function and age. The metabolism of infants is relatively vigorous, water needs are relatively high, 150ml/(kg・d), and then decrease by about 25m1/(kg・d) every 3 years.