Abstract: Magnetic particle flaw detectors are essential nondestructive testing equipment, widely used in the manufacturing industry, typically comprising two current circuits for circumferential and longitudinal magnetization. The accuracy of the magnetizing current is a critical measurement indicator during calibration, serving as a principal parameter ensuring the quality of magnetic particle detection. The standard accuracy grade is generally level 5 or 10. This study addresses the issues encountered during the calibration of the magnetizing current of such detectors and the need for on-site calibration. Considering the current status of high-current measurement technologies both domestically and internationally, we propose an on-line calibration device for magnetic particle flaw detectors based on shunt and Hall sensor sampling. Optimizing the shunt design and employing suitable Hall sensors allows for the calibration of AC/DC circumferential and longitudinal magnetizing currents. Integrated design enables the measurement of magnetizing current operation time, and analysis of basic error, frequency, waveform, and other parameters. We conducted AC/DC circumferential and longitudinal magnetizing current calibration tests on the prototype device, which demonstrated an accuracy level of 0.5, meeting calibration specification requirements. Its simple structure and convenient calibration facilitate on-site online calibration, thereby providing more technical support for enhancing nondestructive testing quality in magnetic particle flaw detectors.