The invention provides an intelligent on-load comprehensive test device for a transformer substation. The device comprises an Ethernet interface unit, a standard voltage conversion unit, a standard current conversion unit, an analog/digital conversion unit, a signal processing unit and a synchronous clock unit, wherein analog three-phase voltage and three-phase current pass through the standard voltage conversion unit and the standard current conversion unit respectively, and then converted into a voltage digital signal and a current digital signal by the analog/digital conversion unit; the synchronous clock unit controls a sampling period of the analog/digital conversion unit; the Ethernet interface unit receives a digitized sampling message; the signal processing unit receives digital signals sent by the analog/digital conversion unit and the Ethernet interface unit, and performs discrete fourier transform directly; and an obtained frequency domain vector can be used for calculating corresponding electric quantity signals, such as effective values and vectors, of the analog and digital signals.