This paper discussed a method of designing soft X-ray multilayers for shorter wavelengths and showed that a difference between the designing of longer wavelength soft X-ray multilayers and that of the shorter one.For the latter,the minimum continuous thickness of the metal layer have to be considered.The method of second order designing could be a way to deposit high-quality multilayer mirrors for shorter wavelengths.The measured reflectivity of a Mo/Si multilayer for 4.47nm is also reported.