The proposed study aims to investigate the effect of surface roughness on the efficiency of diffractive optical elements (DOEs) used in imaging optical systems. A mathematical model describing the influence of surface roughness on diffraction efficiency and polychromatic integral diffraction efficiency (PIDE) is presented, and its effects are analyzed and simulated. Examples of single-layer DOEs containing PMMA substrate and multi-layer DOEs composed of a combination of PMMA and polycarbonate substrates for each layer used in the visible region are analyzed. The results can be used to analyze the effects of surface roughness on the diffraction efficiency and PIDE of DOEs.