Birthmark is not a diagnosis of disease, but a common name for congenital skin abnormality. In fact, birthmarks are only a part of congenital skin abnormalities. Many congenital skin pigment changes do not exist at birth, but appear long after birth. The most common birthmarks on the face are coffee spots, nevus OTA, melanocyte nevus, freckles, brown-blue nevus, nevus flammeus and so on. Can be treated with laser, with a specific wavelength of laser instantaneous excitation, irradiation on the birthmark. Pigment cells or abnormal blood vessels with abnormal birthmarks will absorb the energy of laser and produce thermal effect or explosion. However, normal skin tissue absorbs little laser at this wavelength, so it will hardly be damaged. In various medical beauty institutions, there are many kinds of laser machines of the same type. There is a big difference between high-quality and low-quality laser machines. Poor machines can't control the wavelength, pulse width and energy of laser accurately enough, and it is easy to damage normal skin, so there are many complications and the treatment effect is not good. Therefore, when the treatment effect of an institution is not good, we may wish to consider changing to a good machine for treatment. In addition, there are several common birthmarks, such as hair follicle nevus, sebaceous nevus and cavernous hemangioma. These are difficult to treat by laser alone, and often need laser combined with photosensitizer, medicine or plastic surgery to achieve the goal of eradication.