Abstract： After irradiating the skin,the low-level laser can exert some biological effects,such as photothermal effects,photoimmunological effects and photochemical effects,for the treatment of skin diseases and epidermal vascular diseases.In recent years,with the development of semiconductor laser and light-emitting diode light source,the application of low-level laser therapy in clinic has been gradually increased.The mechanisms underlying skin regulation by monochromatic lights at various wavelengths are different,so different low-level laser should be applied to the treatment of different diseases in clinic,such as skin repair,anti-inflammation and so on.However,the understanding of molecular mechanism of each monochromatic light is insufficient,and the biological regulation pathways are still unclear,so that the clinical application of some low-level monochromatic lights such as green light and yellow light is not widespread,and there was a lack of scientific evidence to support their therapeutic effect.Phototherapy is one of the most important therapies for skin diseases.To learn the progress in treating skin diseases by lowlevel laser at different wavelengths can guide and serve the clinical practice better.