A diffractive optical waveguide and a display device having the same are disclosed, which waveguide comprises a grating structure formed on a surface of a waveguide substrate. The grating structure comprises a plurality of grating lines arranged in a plane, which extend along a first direction in the plane and are arranged at a predetermined interval in a second direction perpendicular to the first direction; at least one sidewall of each grating line has a periodic structure along the first direction; and the grating structure is configured to diffract light incident thereon at a non-zero angle with respect to the plane, out of the plane through a predetermined diffraction order. The grating structure in the diffractive optical waveguide can be used to adjust diffraction efficiency on different angles and/or diffraction orders, thereby providing a new effective and flexible means for improving angular uniformity and/or coupling-out efficiency of the waveguide.