The invention relates to the technical field of three-dimensional display, and discloses an optical grating, a display device and a manufacturing method of the optical grating. The optical grating comprises a first substrate, a second substrate and a polymer layer, wherein the first substrate and the second substrate are arranged oppositely; a first transparent electrode with an optical grating structure is arranged on one surface, towards the second substrate, of the first substrate; a second transparent electrode, which is arranged corresponding to the first transparent electrode, is arranged on one side, towards the first substrate, of the second substrate; the polymer layer is located between the first transparent electrode and the second transparent electrode, and contains nanoscale materials and a liquid crystal elastomer; the nanoscale materials are capable of transforming electromagnetic energy into heat energy; when voltage is exerted to the first transparent electrode and the second transparent electrode, the electromagnetic energy is transformed into heat energy by the nanoscale materials, the polymer layer is in a cholesteric phase and the reflection wavelength is black; and when voltage is not exerted to the first transparent electrode and the second transparent electrode, the polymer layer is in a transparent state. The optical grating is used for combining with the display panel to realize naked eye 3D (three-dimensional) display; and the transmittance loss in 2D (two-dimensional) display is reduced.