Under normal circumstances, children’s urine has no special odor, is light yellow and clear, and slightly precipitates at the bottom when placed at low ambient temperature. However, the shade of urine color is related to the amount of water drunk and sweating. Children who drink more water and sweat less will have more urine and a lighter color, while children who drink less water and sweat more will have less urine and a darker color. However, yellowing of urine in newborns needs to be taken seriously. The yellowing of urine in newborns is divided into physiological and pathological. When a baby is newly born and does not consume enough milk or is dehydrated due to illness, the urine becomes concentrated and the urine becomes yellow in color, while the urine volume decreases. Jaundice is a phenomenon unique to newborns. In some babies with heavy jaundice, in addition to yellowing of the skin and sclera, there is also a phenomenon of deep yellow urine and yellow diaper-stained urine, because excessive bilirubin in the blood circulation is excreted through the urine and dark yellow urine appears. Deep yellow urine, accompanied by fever, fatigue, significant loss of appetite, nausea, vomiting and other discomforts, may be suffering from jaundiced hepatitis. Many mothers think that their baby’s yellow urine is a fire, but for newborns, yellow urine needs to be treated with caution. Yellow urine, accompanied by jaundice, or poor mental status requires prompt medical attention.