An optical waveguide and manufacturing method thereof, display substrate and display device. The optical waveguide comprises an optical fiber array arranged on a surface where each optical fiber in the optical fiber array has a cylindrical shape and the axis of each optical fiber is perpendicular to the surface. With the effect of limitation and mixing of the optical fibers, the intensity and color of the light from the optical waveguide are basically homogeneous in the whole emitting range, such that the viewing angle characteristics of the display device are effectively improved and the problem of uneven brightness and color bias in the range of viewing angle is solved.