The invention discloses a micro polaroid array on basis of metal nanometer optical gratings and a preparation method thereof. The single-layer micro polaroid array comprises a substrate with high light-admitting quality and the metal nanometer optical gratings on the substrate, wherein the arrangement directions of the metal nanometer optical gratings on the substrate are not identical, one optical grating formed by adjacent metal nanowires which are arranged in the same direction is a micro Polaroid, and the size of each micro polaroid is equal to the pixel size of a photosensitive element chip. Meanwhile, the invention further discloses a preparation method for the single-layer micro polaroid array on the basis of the metal nanometer optical gratings. Accordingly, micro polaroid arrays in different polarization directions can be integrated to the same layer, the problem that light transmittance needed by a micro polaroid array based on multi-layer metal optical gratings in the prior art is not high is solved, the technological processes are simplified, and manufacturing cost is reduced.