Photodynamic therapy is a new technology that uses the photodynamic effect for diagnosis and treatment of diseases. It is a photosensitization reaction accompanied by biological effects with the participation of oxygen molecules. The process is that a specific wavelength of laser or intense light irradiation causes the skin tissue absorbed photosensitizer to be excited, and the excited state of the photosensitizer in turn transmits energy to the surrounding oxygen, generating highly active monomorphic oxygen, and the monomorphic oxygen and adjacent biological macromolecules oxidation reaction, resulting in cytotoxic effect, which in turn leads to cell damage or even death, thus treating the new treatment method of relevant skin diseases.