A hardware criterion circuit for single-phase grounding protection line selection comprises a current sampling module and a voltage sampling module, wherein the current sampling module is connected with a first filter circuit; the voltage sampling module is connected with a second filter circuit; the first filter circuit is connected with a differentiating circuit; the second filter circuit is connected with a phase-correcting circuit; the differentiating circuit is connected with a first amplifying circuit; the phase-correcting circuit is connected with a second amplifying circuit; the first amplifying circuit is connected with a current direction judging circuit; the second amplifying circuit is connected with a voltage direction judging circuit; the current direction judging circuit and the voltage direction judging circuit are connected with a power direction judging circuit; the criterion circuit formed by the various circuits is completely triggered by hardware, instantaneous transient power can be captured, and a transient power method is adopted, so that the criterion accuracy is improved; besides, by adopting the hardware, the transient direction can be judged, a single chip microcomputer enters the sleeping mode, the energy consumption demands are reduced, a transient signal can be provided, a multiple criterion manner is supported, the criterion is no longer unitary, and the single-phase grounding judgment accuracy is further fully ensured.