Abstract: With the extensive application of power electronic equipment, the influence of harmonic current increases gradually. The calibration system of current instrument transformer under harmonic conditions needs to develop to meet needs of measurement capacity. However, traditional calibration equipment can only be utilized to perform tests at power frequency. To solve the problem in measurement characteristic tests of current instrument transformer under harmonic conditions, a wideband current transformer error calibration system is proposed and developed based on high-accuracy active compensation current transformation method. The high-accuracy current transformation section is emphatically introduced in this paper. First, based on the active compensation method, a wideband zero-flux current transformer is designed, and its theoretical model is developed. Moreover, a wideband compensation method of traditional trans-impedance amplifier is proposed. In the circuit loop, an in-phase amplifier is added, and the compensation effect is theoretically calculated and simulated. The compensation method can be adopted to significantly reduce the amplitude and phase errors of the trans-impedance amplifier. The test results indicate that the measurement uncertainty of the calibration system under power frequency is 2.6×10^-6 and 2.1 μrad, respectively, and, the uncertainty is 30×10^-6 and 20 μrad within the range of 10 kHz, respectively.