Abstract: In order to define the optimum design of the X-ray defector for meeting the requirement of the coal and gangue separation system,a comparison is made between the array ionchamber type detector and the scintillation version based on the attenuation of continuous energy spectrum X-ray in relation to the presence of gangue in coal.Based on the result of comparison,the former type is selected for use.The paper presents an introduction to the external form,internal structure,technical parameters,working principle and technical features of the detector.Result of study shows that,because of the presence of a perforated partition plate in the ionchamber,the detector can perform dual-energy detection function with its highenergy and low-energy chambers,and both the 2 chambers can work with the same detection efficiency.The detector is simple in structural design,reliable in performance,and is particularly suitable for use under harsh conditions.