Abstract: This paper presents a mask fabrication method, which uses laser interference lithography to prepare interference patterns, and then transfers the patterns to the chromium layer by ion beam etching (IBE) to gain the mask. A series of rigorous numerical simulations have been done on the light transmission rate of the mask and two parameters that may affect the contrast of interference patterns for parameter optimization. An interference lithography system was constructed with 257 nm laser light source, and patterns with feature size of 100 nm were developed. Then masks with period of 200 nm and line width of 100 nm were obtained by IBE.