The fabrication process of holographic lithography micro-nano gratings using metal masks is designed and optimized. First, an 860 nm periodic grating is prepared using holographic lithography and inductively coupled plasma (ICP) dry etching on the GaAs substrate. The hard metal mask grown by magnetron sputtering is introduced into the etching process as a barrier layer for grating etching and the Ni mask is fabricated by the lift-off method. It has been shown that when photoresist, SiO₂, and Ni are used as masks for ICP dry etching, they determine the etching depth and morphology of the grating. Results show that the Ni mask has strong etch resistance. Scanning electron microscopy demonstrates that Ni with a thickness of 50 nm can be used as a hard mask to create a grating with an aspect ratio of about 4.9. The grating has a groove width and etching depth of 300 nm and 1454 nm, respectively, with steep sidewall morphology and good periodicity and uniformity.