In this paper, the crystal spectrograph used to investigate long wavelength softX-ray spectroscopy of laser-produced plasmas was described. The laser plasmam soft X-ray spectra with wavelength up to 5.8 nm have been taken by using OHM crystal (2d=6.35 nm), combining with very thin carbon filter (310 nm in thickness) and soft X-raysensitive film (SIOFM-5FW). The measured spectral resolution of the spectrograph wasalso given.