Abstract: Based on the GEANT4 toolkit and an X ray machine whose maximum tube voltage was 225kV, the characteristic changes of the gain, the detection efficiency and also the spatial resolution of the Xray detector were studied through the working voltage and geometric parameters of the microchannel plate under different incident energies. It can provide a reference for practical application. Study confirms that the microchannel plate detector can meet the requirement of industrial CT system proving the following settings are met: the micro pore diameter of 20μm, length to diameter ratio of 40, the opening area of 60%, angle of 8°, working voltage of 970V and the working environment of vacuum degree 10-3Pa.