The invention discloses a digital virtual step-out relay which finally sends out an action signal or a holding signal through a series of processing processes of the measuring data of the PMU by a processor, and belongs to the technical field of power system relay protection. The hardware of the relay is provided with a data acquisition module, an STM32F107, a digital-to-analog conversion module and an associated external interface, the external hardware comprises a GPS receiver, a rotor position sensor, a voltage transformer, and a current transformer. The relay provided prevents the complicated calculation and analysis of the setting value of a traditional impedance type out-of-step relay, and prevents the problem that the Fourier transformation method in the prior art is serious in error, and the technical problems that in the prior art, the cost is high, the accuracy rate is low and the real-time monitoring cannot be achieved are solved.