The clinic encounters many parents of boys who ask if their child’s penis is too small and needs to be treated. In fact, penis size and length vary from person to person and are not a customized product. Penis size varies greatly depending on whether the penis is engorged or not. Pre-pubertal development of small penis is defined as the absolute value of penile elongation is less than 2.5 cm, or shorter than the same age, the same race of children 2.5sd (standard value), the penile structural type of normal. However, we need to distinguish it from cryptogenic penis. Concealed penis is due to the rich subcutaneous fat in front of the toe bone, the penis skin attached to the penis is relatively insufficient, so that the normal size of the penis is buried in the subcutaneous fat, from the appearance of the penis appears to be short. If we move the skin at the base of the penis backward and compress the fat, the hidden penis will be revealed.