The He-Ⅱ spectrum at the wavelength of 30.4 nm is a key spectrum in extreme ultraviolet astronomic observation, and multilayer film reflective mirror are usually adapted in the observation. The reflection at the wavelength of 30.4 nm of the multilayer films composed of SiC/Mg, B4C/Mg, C/Mg, C/Al, Mo/Si, B4C/SI, SiC/Si, C/Si, Sc/Si is studied. Based on the optimization of largest reflectivity and narrowest width for the multilayer film mirror, SiC/Mg multilayer is selected as the film material, SiC/Mg multilayer films are fabricated by using magnetron sputtering. The periodical thickness of the SiC/Mg multilayer film is measured by X-ray diffractometer, and the reflectivity was measured by the reflectometer in synchrotron radiation laboratory. At incidence angle of 12°, the reflectivity of 38.0% is obtained at the wavelength of 30.4 nm.