Abstract: A 7-channel hard X-ray spectrometer was designed for measuring the photon energy distribution of the hard X-ray emitting from the loads used in Z-pinch experiments on PTS. In this paper, we present the measuring principle, configuration, measuring parameter and the unfolding method of the spectrometer. We tested our spectrometer on PTS machine, detected the hard X-rays produced during Z-pinch and acquired the signal curves of high signal-to-noise ratio. The maximum entropy method was employed in unfolding these curves and the spectrum of the X-ray radiation was obtained. The result of unfolding indicates that the hard X-ray radiation distributed mainly in 200-500 keV, rarely over 1 MeV.