A flat-field grating spectrograph with one demension spatial resolution was developed. The speotrograph, consisted of a grazing incidence collecting optics combined with a cylindrical mirror and a spherical mirror, and a variable line-spacing concave grating, has not only the advantages of easy adjustment, higher efficiency and higher spectral resolution, but also the capability to provide one demensional spatially resolved spectrum simutaneously over 4.4-30nm wavelength range. The spatially resolved on-axis spectra of Si, Cu and other element plasmas produced by line-focused laser were successfully obtained. Such a spectrograph is suitable for coupling with the detectors having flat receiving surface, such as soft X-ray streak camera, to achieve the time-resolved XUV spectra.