Skin cancer has a low incidence in our country, but is one of the common malignant tumors among the white population, exceeding all other malignant tumors combined. In southern Australia, the incidence rate of skin cancer is at least 650/100,000, and among Caucasians in the United States, the incidence rate of skin cancer is as high as 165/100,000, which is 100 times of the incidence rate in China. The early manifestation of skin cancer is mostly erythematous lesions with scaly flaking or scab formation, which is difficult to distinguish its histological type by visual observation alone and easily confused with benign skin diseases such as psoriasis and eczema. Regardless of surgery, radiotherapy or other treatment methods, all of them have good efficacy on skin cancer, and the cure rate can be over 90%. There is sufficient evidence to support the occurrence of skin cancer due to the interaction between the protection of human melanin and the function of immune system, and the measurement of human skin in daylight, the parts of skin receiving the largest amount of UV are head, face, back of neck and hands, and almost all squamous cell carcinomas occur in these parts. The mechanism of UV carcinogenesis may be that photochemical action changes the structure of cellular DNA, and at the same time destroys the active antigen structure on the surface of lymphocytes, which reduces the immune function of the body and leads to the occurrence of skin cancer with the joint participation of other cancer-promoting factors. 2.Chemical carcinogens: About 100 years after Percivall first described that chimney sweepers are prone to scrotal skin cancer, it was found that workers who are frequently exposed to arsenic, tar and asphalt are prone to skin cancer, and chemical carcinogenesis can be divided into two periods, i.e. the initiation period and the help period. The interval between the beginning and the end is very important, and two kinds of results can occur, i.e. skin cancer can be formed or not. 3.Ionizing radiation: Skin cancer occurred in the past on the basis of radiation dry skin due to the neglect of protective measures by radiation workers for a long time. However, some patients who received radiation treatment can still develop skin cancer in the radiation field after several years. 4.Chronic irritation and inflammation: Malignant skin tumors can occur and develop in the areas of scarring, chronic ulcers, fistulas and sinus tracts, and some Asian people are fond of chewing tobacco or betel nut, so squamous cell carcinoma is prone to occur in the oral cavity or lip area. 5.Other: Immunosuppression stage, patients with low immune system function, skin cancer can occur, such as the application of immunosuppressants can contribute to the occurrence of skin cancer, viral carcinogens, many viruses in animal hosts can cause cancer, many subtypes of human papilloma virus in humans can induce skin cancer.