Babies three years old can distinguish whether the circumcision through physical examination, other auxiliary examination and other ways. 1. Physical examination: usually the diagnosis of prepuce relies on physical examination, usually physiological prepuce baby in the upturning of the narrow opening of the foreskin, can be seen part of the reddish, good elasticity of the inner plate of the foreskin. While the pathological circumcision of the baby in the examination, can be seen in the circumcision of the mouth of the scar hyperplasia or fibrosis formation. 2. Auxiliary examination: for other auxiliary examination, the main items include blood routine, urine routine and so on, which are used to determine whether there is infection and other conditions. For simple phimosis, the outer opening of the foreskin is generally loose, and the foreskin can be turned back and upward, so that the head of the penis can be easily exposed; while for hidden penis, it is mainly seen in obese people, the appearance of the foreskin is in the shape of a bird’s beak, and the body of the penis can be exposed when the skin of the penis is squeezed to the inner side. Usually, the foreskin needs to be differentiated from the above two diseases. Parents are advised to bring their children to regular hospitals for examination in order to clarify whether the prepuce and its type are present. Personal hygiene should be strengthened by changing underwear frequently, choosing cotton underwear as much as possible, and using warm water to clean the area every night.