Sweating a lot when a 3 year old baby falls asleep is overwhelmingly a normal physiological phenomenon. the function of the vegetative nervous system dominates during sleep in a 3 year old baby, which can lead to excessive sweating. This situation is related to the age of infants and young children, because infants and young children’s metabolism is more vigorous, high basal metabolic rate, easy to have excessive sweating phenomenon. Most infants and young children show increased excitability of the brain nervous system during light sleep, and sweat a lot during sleep. After an hour or so, the sweating phenomenon will get better when the child enters deep sleep. However, if individual children have excessive sweating, clinical attention should be paid to whether it is accompanied by other conditions, for example, calcium deficiency can also cause excessive sweating, but it will be accompanied by sleep disturbance, easy to cry, and blood calcium is lower than normal, etc. Clinical need to take vitamin D and calcium gluconate supplementation to assist in the treatment.