Single diamond turning is usually used to fabricate multilayer diffractive optical elements (MLDOEs). The choice of diamond tools directly influences the profile error and surface roughness error of MLDOEs. Those two errors will cause the shadowing effect and scattering effect, which decrease the diffraction efficiency of MLDOEs. The relationship among diffraction efficiency, cutting tool radius, feed rate, and microstructure periods was presented. A model to find the optimal cutting tool radius and feed rate before the fabrication was put forward to balance the influence of shadowing effect and scattering effect, which can maximize the polychromatic integral diffraction efficiency. The effect of diamond cutting tool radius and feed rate in the manufacturing process of MLDOEs is discussed and analyzed numerically, and the results will be intended as guidelines for manufacture of MLDOEs to achieve diffractive surface-relief profile with high quality.