The invention discloses an electronic current transformer calibrating device. Two current sources respectively transmit current signals A1 and A2, wherein, the A1 is bigger than the A2 and has different frequency from the A2. A reference transformer senses the A1 and the A2 which is amplified by N folds simultaneously, and a tested transformer senses the A1. A merging unit transmits a synchronization pulse signal to the reference transformer, the tested transformer and an AD converter simultaneously, obtains digital quantities of current sampling values of the reference transformer and the tested transformer and the digital quantity of the voltage value at the two ends of a sampling resistor which is obtained by conversion with a reference AD converter at the falling edge of the synchronization pulse signal, and synthesizes the digital quantities into a data frame and sends the data frame to a control computer. The control computer compares the current signal which is obtained by sensing the A1 by the reference transformer with the current signal output by the tested transformer, calibrates the scale difference and the angular difference of the tested transformer, compares the current signal which is obtained by sensing NA2 by the reference transformer with the current signal which is obtained by converting the output voltage from the reference AD converter, and performs self calibration on the reference transformer.