Abstract: The diffraction efficiency of a diffractive optical element(DOE) was analyzed with an additional phase introduced by an antireflection film, and the optimum design method of a DOE with an antireflection film was proposed. For a DOE working within the visible waveband, the diffraction efficiency was compared and analyzed using the proposed optimal method and traditional method. The results showed that the influence of the antireflection film on the diffraction efficiency and the bandwidth integral average diffraction efficiency(BIADE) of the DOE is not negligible. For the two working states of normal incidence and 30° oblique incidence, the BIADE of the DOE obtained by the optimal design method was higher than 94%.