Penile prepuce is a phenomenon in which the foreskin is narrowed or adhered to the head of the penis so that the foreskin completely covers the head of the penis and cannot be turned up to the coronal groove of the penis. The change in appearance of penile prepuce in children is mainly divided into two stages, namely the physiological prepuce period (0-3 years old) and the prepuce relaxation period (after 3 years old).1. Physiological prepuce period: At this time, the prepuce is manifested by the existence of congenital adhesions between the foreskin and the glans, and the prepuce opening is small and wraps around the penis head, forming a natural narrow ring. The child’s foreskin is difficult to be turned up to expose the head of the penis, and erection cannot expose the head of the penis and the urethra. The skin of the outer plate of the foreskin is long and elastic, while the inner plate cannot be exposed. Because the opening of the foreskin is small and pinpoint, the foreskin may bulge and swell when the child urinates, and then return to its original state after urination. This is the stage of prepuce that all children have to go through. At this time, prepuce does not need special treatment; 2. The period of prepuce relaxation: after children are 3 years old, the adhesion zone where the prepuce is located gradually loosens and softens, at this time, the narrow ring will gradually loosen and soften, and the appearance of the prepuce will show that the outer plate is partly loose and extended. The glans is fully exposed. If parents usually do not help children to turn up the foreskin to clean the glans, or children are afraid to turn up because the foreskin mouth is too small and afraid of pain, it will easily cause the accumulation of foreskin scale, and when the weather changes or children’s resistance is low, the penis is covered by underwear or diapers, which will easily cause bacteria to accumulate and grow, resulting in inflammation and pus at the outer foreskin.