Abstract: The principle, structure, and adjustment of a flat field grating spectrograph are presented. A varied line space grating with no minal line spacing 1200L/mm is used in this spectrograph, The incidence angle is 87℃, and spectral range of detection is 5～30 nm. Both experimental results of the instrument for time integrating detection using the film and time resoluting detection using a streak camera are presented as well.The spectral resolution are 0.Olnm and O.05nm, respectively. The temporal resolution is ～30ps. Finally, the evaluation is given.