Insulation technology of high voltage electrical equipment is a must be used in high voltage electrical equipment, the use of high-voltage electrical equipment insulation technology can ensure the safety and stability of power equipment supply. In the power supply, the application of high voltage electrical equipment insulation technology should be used to detect the operation of equipment. Therefore, the insulation technology of high voltage electrical equipment occupies an important position in the power system. In order to prevent the accident of insulation safety, the traditional practice is to carry out preventive test and maintenance after the equipment is put into operation, so as to detect the insulation defects in the equipment in time. But the test condition and the running state of the preventive test of power cut have great difference, so the insulation condition of the transformer can not be accurately diagnosed. Therefore, it is necessary to make a thorough research on the calibration method of the insulation on-line monitoring device of substation equipment. We hope to provide some valuable reference for the more effective use of the insulation technology of high voltage electrical equipment.