When voltage transformer error-site of GIS is calibrated, due to the uncertainty of its distributed capacitance, the conventional test methods exist boost difficulties and operating complex issues. Based on the technology of first FM then modulation inductance and years of experience in the field, this article designs and implements intelligent calibration systemSfor voltage transformer error-site of Gis, introduces the composition and implementation program of calibration system, gives structural design method of a high-pressure adjustable reactor, introduces hardware and software design methods of the intelligent inverter control power. Several experiments show that the calibration system can calculate distributed capacity of tested voltage transformer in a Low voltage FM resonance manner, automatically adjust the high pressure adjustable reactor inductance, automatically complete resonance boosting and error calibrating, can improve the technical level of on-site test and the working efficiency. Thus the calibration system was checked by the relevant authorities in July 2013.