The invention relates to a technical field, and especially relates to a testing method for a legal metering part of a double-core electric energy meter. The method comprises the steps that a detection table body receives an instruction of a PC, and outputs a signal to a detected electric energy meter; the detection table body obtains the metering data of the legal metering part of the detected electric energy meter under a plurality of testing conditions, and calculates error data according to metering data; the PC stores the error data, and carries out the fitting of an error curve according to the error data; the PC compares the error curve with a calibration standard, and obtains a comparison result. Because the detection table body calculates error data according to metering data, the PC stores the error data, and carries out the fitting of the error curve according to the error data, compares the error curve with the calibration standard, and obtains the comparison result. The method can detect the accuracy of independent operation of the legal metering part of the detected electric energy meter under the interference of various types of testing conditions.