The invention discloses a calibration system and a calibration method of an alternating large current of a current transformer. The calibration system of the alternating large current of the current transformer comprises a large current sensing unit, a data collection unit and a personal computer (PC), wherein the large current sensing unit comprises an iron core coil, a hollow coil, a signal conditioning unit and a shielding case, the hollow coil and the signal conditioning unit are fixed inside the shielding case, the iron core coil, the hollow coil and the shielding case are respectively installed on a current-carrying wire, a first bypass wire is arranged between the iron coil and the hollow coil, and an output end of the signal conditioning unit is connected with the PC through the data collection unit. Mutual inductance coefficients of the installed hollow coil are calibrated through the iron core coil, whether a state of the hollow coil meets a calibration condition or not is judged, closed-loop control when calibration is conducted is finished through feedback of the mutual inductance coefficients of the hollow coil, the high-accuracy calibration on the alternating large current is achieved, and output accuracy of the current transformer with the hollow coil is ensured.