The utility model relates to a current transformer with from calibration functions device, current transformer includes iron core, side winding coil, secondary -side winding coil, switch, resistance and a display element, wherein: the secondary -side winding coil comprises the duplex winding, the parallel duplex winding of two secondary winding interlude formula, and the number of turns is unanimous, and the line footpath is unanimous, the switch is established ties with it after two secondary winding are parallelly connected, resistance is established ties with the switch, just resistance is the non -inductive resistance of coiling, and the resistance after parallelly connected equals that display element is used for the current value of monitoring current mutual -inductor secondary side output when the fortune state with two secondary winding for the resistance of resistance.