Children are always thirsty and appear to drink a lot of water, first of all, we should exclude the food caused by drinking a lot of water, to find out whether the food is eaten too salty, too sweet, or eat too much fried food, can cause thirst. Secondly, there is physiologic polydipsia, also known as psychogenic polydipsia. Most children start to experience thirst and polydipsia after one infection, and then form the habit of drinking more water. The following diseases should be excluded: the first disease is diabetes mellitus, which is accompanied by eating more food, urinating more, and losing weight in addition to drinking more water. The second disease is uremia, in addition to thirst, drinking more will also appear to increase the amount of urine, urine volume of up to 4000-10000ml. The third disease is hyperthyroidism, hyperthyroidism patients in the early stage of drinking, eating, sweating, irritability as the main manifestations, so if there is more drinking, should also be excluded hyperthyroidism.