Background: Electron temperature is one of most important parameters in the controlled magnetic confinement fusion experiments. Purpose: We attempt to develop a set of soft X-ray energy spectrum diagnostic system for measuring the plasma soft X-ray (1?30 keV) spectra on Experimental Advanced Superconducting Tokamak (EAST). Methods: The diagnostic system is based on a 10-element Silicon Drift Detector (SDD) array and fast electronics

and basically views lower half-space of the plasma. Results: The diagnostic system can measure electron temperature under various plasma configuration conditions and the electron temperature obtained from the system is consistent with electron circle emission (ECE) and X-ray crystal spectrometer (XCS) diagnostic systems. And the system can monitor the middle and high Z impurities in the plasma as the good energy resolution of the system. Conclusion: The diagnostic system had been installed on EAST and verified its reliability and effectiveness and gained the good experimental results. Abstract