The disclosure provides a design method of a coupling-out grating of an AR optical waveguide, the AR optical waveguide including a coupling-in grating, an optical waveguide body and the coupling-out grating, and the design method including: S101: calculating a diffraction coupling-in angle, at which a light beam is diffracted and coupled into the optical waveguide body through the coupling-in grating, according to an angle at which the light beam is incident to the coupling-in grating, a wavelength of the light beam and a grating period of the coupling-in grating; S102: calculating a distance between two adjacent coupling-out positions of the light beam on the coupling-out grating according to the diffraction coupling-in angle and a thickness of the optical waveguide body; S103: calculating a brightness difference rate of the light beam after being coupled out multiple times through the coupling-out grating according to the maximum diffraction efficiency of the coupling-out grating; and S104: calculating the number of partitions of the coupling-out grating according to a length of the coupling-out grating, a sensitivity of a human eye to the light beam, the brightness difference rate, and the distance between the two adjacent coupling-out positions.