For the diffractive optical elements (DOEs) in imaging optical systems, a range of incident angles is the normal working situation, and the introduction of antireflection coatings (ARCs) to DOEs affects polychromatic integral diffraction efficiency (PIDE). Relying on the phase function of DOEs, we modify the microstructure heights with ARCs in this paper. Furthermore, we build theoretical models of the relationship between the comprehensive PIDE and modified microstructure heights of single-layer and multilayer DOEs working within a certain incident angle range. With DOEs working in the infrared waveband as an example, we comparatively analyze the diffraction efficiency and PIDE with ARCs designed by the common method (CM) of maximizing the PIDE to obtain microstructure heights and by the proposed modified method (MM) based on modified microstructure heights. The simulation and calculation results show that both the change in incident angles and optical thicknesses of ARCs will induce the decline in the PIDE of DOEs with ARCs. With the MM, the comprehensive PIDE is 95.528% and 99.449%, respectively for single layer DOEs with a substrate of ZnSe working in the incident angle range of 0°-30° and multilayer DOEs in the 0°-20° range. This method provides a reference for the optimal design of DOEs.