A high spectral-resolution solar Far-Ultravoilet/Ultraviolet (FUV/UV) spectrometer carried by high-altitude balloons to the bottom region of the near space was designed, which will historically fill the data gap in wavelength shorter than 280 nm that deposits engergy in this region. The solar FUV/UV spectrometer is based on improved Roland circle optics. In order to adapt to the requirements of high-altitude balloon platforms, it has a compact design for the optics to reduce the dimensions of the instrument, to suppress the spherical aberration of the optical system, and to improve the quality of the spectrum. The optical performance was simulated by the Zemax software to analyze the spectral resolution, wavelength coverage, and stray light suppression.