Abstract: It is not clear whether high energy X-ray will cause deterioration of insulating material when X-ray imaging technology is adopted for visual inspection of bulky electrical equipment. In order to study the effects of X-ray irradiation on the properties of insulating materials, an X-ray source with a maximum tube voltage of 225 kV was used to irradiate epoxy/alumina (EP/Al₂O₃) under air and sulfur hexafluoride (SF₆) atmosphere, respectively. After X-ray irradiation at different time, the influence of irradiation conditions on insulation properties was analyzed systematically. Only slight degradation in insulating performance was found although the dielectric properties and volume resistivity of EP/Al₂O₃ after 10 min X-ray irradiation began to deteriorate. In addition, high-energy X-ray irradiation makes the trap energy level inside the insulation material shallow or even produces obvious shallow traps, which intensifies the surface charge decay degree and rate, helps dissipate the space charge on the surface of the insulation device, and is conducive to maintaining the insulation safety of the power equipment.