On the basis of the equivalent-medium theory and the body phase delay of multi-layer diffractive optical elements, considering the influences of phase modulation caused by antireflection films, the surface microstructural parameters of multi-layer diffractive optical elements are optimized to realize the diffraction efficiency of 100% at the design wavelengths and the high polychromatic integral diffraction efficiency within a broad waveband. With this optimal design method, the diffraction efficiency and polychromatic integral diffraction efficiency of multi-layer diffractive optical elements with antireflection films working in visible wavebands are analyzed. The results show that with this optimal design method, the diffraction efficiency of 100% at the designed wavelengths and the high polychromatic integral diffraction efficiency within a broad waveband can be achieved under the premise of ensuring the physical effects of antireflection films. This method makes up for the traditional design defects of multi-layer diffractive optical elements and improves the design theory of multi-layer diffractive optical elements, which provides a reference for the design of hybrid imaging systems.