With the development of microelectronics technology, it is necessary to study the fabrication process for high aspect ratio and a vertical sidewalls micro-nanostructures on the substrate. High quality nano master grating can be fabricated by X-rays lithography. By using sophisticated nano electroforming technology, high-quality nano metal grating can be replicated from the mother mold grating. A technique for preparing high aspect ratio diffraction grating metal molds is introduced. Based on synchrotron radiation lithography technique, polymethyl methacrylate (PMMA) nano gratings with line width of 0.25, 0.5, 1 μm, and the height of 2.0 μm are prepared on a silicon substrate. Using precision electroforming technique, nickel nano-grating mold with the line width of 0.25, 0.5, 1 μm, and the 1 μm gratings aspect ratio of 1.5 is fabricated from the PMMA grating master mold. In order to obtain high-quality PMMA nano-grating, the adhesive is used to overcome the deficiencies of structures collapsed, by optimizing exposure parameters, small triangular structures at the bottom of the gratings are eliminated.