Abstract: In order to get a 1-step rainbow hologram with large square and wide viewing field, one must place the slit at the imaging lens and use divergent waves as the reference wave and reconstruction wave.For this purpose, the apertureconjugation technique is introduced. The combination of the aspherical leases with large aperture and large relative aperture is used to obtain large viewing angle, wide observation range and high quality of image for the hologram. A 1-step rainbow hologram with the square of 400 mm x 400 mm has been successfully made, the making process and the key technique for the hologram is described in the paper. Finally, the position and the length of the image of the slit, the depth of field, the color blurring and the image blurring,the diffraction efficiency and the influence of Bragg effect on the reconstruction image are discussed.