Red light is visible light with a wavelength range of 620-760 nm, which has excellent photochemical and thermal effects. It can penetrate deeply into the skin and tissues with strong power, resulting in a series of biological effects. In the field of ophthalmology, red-light therapy was initially mainly used in the treatment of amblyopia and eyelid skin-related diseases, and with the further development of research, red light has been gradually used in the myopia control and the study of retina-related diseases. At present, the effect of repeated low-intensity red light (RLRL) on myopia progression has been fully recognized, and it has become one of the most concerned hotspots in the application of red-light therapy in ophthalmology. The main possible mechanisms include that red light therapy can activate the activity of cytochrome C oxidase in mitochondria, promote ATP production, and improve retinal hypoxia. It can also induce the synthesis and release of NO, cause the expansion of choroidal vessels with improvement of blood flow, and increase scleral strength by remodeling of scleral extracellular matrix. In addition, red- light therapy can reduce oxidative stress, inflammation and apoptosis in the regulatory pathways of photoreceptor cells, reduce eye inflammation and pain, and help repair peripheral nerves after injury. This article will review the mechanism, effectiveness and safety of red-light therapy in myopia, retinal diseases, amblyopia, and eyelid skin-related diseases, in order to provide important reference value and basis for the application of red-light therapy in ophthalmology.