Based on the expression between diffraction efficiency and incident angle and the expression between diffraction efficiency and micro-structure height error under normal incidence, the mathematical relationship between micro-structure height error and diffraction efficiency or polychromatic integral diffraction efficiency (PIDE) for diffractive optical elements (DOEs) under oblique incidence is established. When the absolute value of the relative micro-structure height errors is equal, the corresponding diffraction efficiency and PIDE with negative micro-structure height errors are higher than those with positive micro-structure height errors. The analysis method and conclusion provide a theoretical reference for the determination of the machining tolerance of micro-structure height error for DOEs.