With the popularization of digital transformer substations, it is of great research significance to study the upgrade of electronic transformer calibration devices, especially in the scene of small signals and high precision. In this paper, a compensation correction method is proposed to obtain more accurate primary side current parameters of the tuning device. By establishing the J-A magnetic characteristic model of the CT, the relationship between the magnetic characteristics of the CT and the corresponding terminal voltage is analyzed, and the relationship model between the terminal voltage and the corresponding excitation current is established. The model is used as the correction value in the feedback loop of the current measurement of the integral inspection device, to obtain the accurate primary side current. This method is applied to an electronic transformer calibrator inspection device system based on the Beidou system, which improves the data measurement accuracy of the device sensor and ensures that the measurement data accuracy reaches 0.1S.