There are many types of moles in children, either congenital moles or acquired moles. Congenital moles are mostly related to heredity, subcutaneous melanin growth or capillary malformation, while acquired moles are mostly related to UV exposure in the environment. Congenital nevi are divided into various types of lesions such as pigmented nevi and hemangiomas, which may vary in appearance and grow in different areas, and the prognosis may also vary. If a child’s mole is not in a special place, no special treatment is needed; if a mole is in a special place and suddenly appears to increase in size or darken in color, or if there is erosion, ulceration or bleeding on the surface, and if the child feels pain and itching, he or she needs to go to the hospital promptly and if necessary, laser or even surgical treatment can be performed. When human skin is exposed to relatively strong ultraviolet rays, some melanocytes will suddenly become active and also form pigmented nevi on the human body, which are acquired nevi. Pigmented nevus may develop malignant lesions, but the incidence is not high, only in some special cases and special parts need to be paid high attention, such as friction parts or parts prone to skin damage, early intervention can be properly considered, pathological examination can be conducted if necessary, and if there is a tendency of malignant transformation, timely surgical removal is needed.