The invention discloses a high refractive index contrast grating and preparation method and application thereof. The high refractive index contrast grating comprises a transparent substrate and a highrefractive index contrast monocrystalline silicon grating, wherein the high refractive index contrast grating has high transmittance and covers a phase change of 0 to 2pi in a visible light band. According to the high refractive index contrast grating and preparation method and application thereof, the grating is designed by adopting the high refractive index contrast monocrystalline silicon material the low aspect ratio can be realized through reasonable size design, and the loss in the visible light band is small, so that a plurality of functional devices with low loss in the visible lightband, such as deflectors, vortex light generators, focusing lenses and the like, can be prepared by using the high refractive index contrast monocrystalline silicon material.