We have developed an objective soft x-ray flat-field spectrograph installed in electron microscopes (EMs). The spectrograph has two attractive features. One is that it is designed to cover a wide energy range of 50-4000 eV by using four varied-line-spacing holographic gratings (VLSHGs) optimized for 50-200 eV, 155-350 eV, 300-2200 eV, and 2000-4000 eV. The gratings dedicated for the respective energy ranges can be accommodated in the single spectrograph. This advantage comes from that the positions of the source points and image planes are assumed as the common parameters in the design of all gratings. Therefore, it allows to easily change the energy range by only choosing an appropriate grating and its position. The other is the application of a newly invented W/B4C multilayer coating. It has been adopted to the grating for the 2000-4000 eV range to overcome the considerable decrease of the diffraction efficiency in the energy range above ∼2 keV. The novel coating makes it possible to enhance uniformly the diffraction efficiency at a constant incidence angle in the whole energy range.