Abstract: In this paper we briefly introduce the construction and the basic principle of a subkeV X-ray spectrometer composed of a filtered XRD array with fast time response. The energy resolution is about 200eV in the range of 0.1-1.5keV. The application of this spectrometer and data precessing are presented. The subkeV X-ray spectrum and radiation temperature are given from the data obtained in experiments of laser-Au planar target inferaction.