Giant nevus, also known as giant congenital melanocytic nevus, is characterized by a huge nevus area. Generally, an adult nevus with an area of 3600px2 or more, or a diameter of more than 500px, can meet the diagnostic criteria. Of course, the diagnosis of giant nevus cannot be completely dependent on the absolute area size, but should also be combined with the patient’s body surface area. Giant nevi are usually present at birth and can appear on the entire limb, head, face, and most of the trunk, brown or black, soft, uneven, rough, hypertrophic, with hair growth, and many scattered satellite lesions in the periphery. Giant nevi have the potential to become malignant, but the rate of malignancy is inconsistent and patients are generally advised to have them removed as soon as possible. The skin defect after removal of giant nevus usually requires skin grafting, but the grafting area is huge, the amount of skin in the donor area is insufficient, and scarring is left behind, making treatment difficult and ineffective. Plastic surgery specialties often use soft tissue dilation to repair post-excision giant nevus defects. Soft tissue skin dilation, which originated in the 1980s, is widely used in the field of plastic surgery treatment. A skin soft tissue expander is implanted under the normal skin soft tissue around the lesion, and saline is injected into the expansion capsule through an injection jug to increase the expansion volume and tension on the surface skin soft tissue, which causes the division and proliferation of tissue and epidermal cells and enlarges the cell gap, thus increasing the skin area and using the newly increased skin soft tissue for tissue repair. The skin expansion method also has certain requirements for the treatment of giant nevus. It is mainly applied when there is a certain amount of normal skin around the giant nevus, and sufficient and effective skin expansion can be performed to have a better treatment effect. The procedure is usually performed in two times, the first time the skin expander is implanted under the normal skin, the second time the lesion is excised after the skin is fully expanded, the expander is removed and the expanded skin is used for repair. The time between the two surgeries is the process of water injection and expansion, which usually takes 1 to 3 months.