Lichen planus is a skin lesion caused by human papilloma virus infection. It occurs on the face and back of the hands of young people. It is not only a chronic viral disease but also a troublesome cosmetic problem. Traditional treatment methods have low lesion clearance rate, poor tissue selectivity, irritation, and scarring, making it difficult to meet the treatment requirements of patients, making the disease a common and persistent disease in dermatology. Photodynamic therapy is a new type of tissue ablation therapy with the advantages of less trauma, faster onset of action and no scar formation because the photosensitizer can be selectively absorbed by the virus-infected cells. A number of clinical studies show that photodynamic therapy for the treatment of facial flat warts, after 1 to 5 courses of treatment, wart clearance rate of 95% to 100%, the majority of patients and clinicians recognized, become a strong choice for patients with persistent facial flat warts!