The invention discloses a double-layer fiber reinforced plastic grating and a preparation method thereof, and relates to the technical field of fiber reinforced plastic gratings, wherein the double-layer fiber reinforced plastic grating comprises two layers, the outer layer is a conventional double-layer fiber reinforced plastic grating material layer, and the inner layer is a filler layer. According to the present invention, the anti-impact modifier is added to the outer layer raw material so as to significantly improve the high impact resistance and the high tolerance of the double-layer fiber reinforced plastic grating; by adding the inner layer filler, the microscopic loose structure of the double-layer fiber reinforced plastic grating tends to be dense so as to further improve the toughness of the double-layer fiber reinforced plastic grating; and the wear resistance and the service life of the fiber reinforced plastic grating can be significantly improved through the outer layermaterial of the double-layer fiber reinforced plastic grating.