Abstract: The present disclosure provides a direct current (DC) transformer error detection apparatus for a pulsating harmonic signal, including a DC and pulsating harmonic current output module and an external detected input module, where the DC and pulsating harmonic current output module outputs a DC and a DC superimposed pulsating harmonic current to an internal sampling circuit and a self-calibrated standard resistor array; and the internal sampling circuit converts the input DC and the input DC superimposed pulsating harmonic current into a voltage signal, and sends the voltage signal to an analog-to-digital (AD) sampling and measurement component through a front-end conditioning circuit and a detected input channel. The DC transformer error detection apparatus can complete self-calibration for measurement of the DC and the pulsating harmonic signal on a test site.