We report the design, construction, and commissioning of a spectrometer for non-resonant inelastic x-ray scattering study installed at BL15U, Shanghai Synchrotron Radiation Facility. It features a 1-m vertical scattering arm. An energy resolution of 1.3 eV is achieved based on the 1m Rowland circle and the diced Si(555) crystal analyzer with a fixed Bragg angle of about 88.8 degrees. The inelastic squared form factors of 2(1)S + 2(1)P of helium with respect to the momentum transfer were measured and compared with the accurate and reliable theoretical calculations in order to verify the spectrometer. Furthermore, the spectrometer is designed to work in the momentum transfer region of 0 angstrom(-1) < q < 8.68 angstrom(-1) and to initially focus on the non-resonant inelastic x-ray scattering studies on gaseous samples. Published by AIP Publishing.