The proposed invention discloses a safe processing method for active voltage reduction of a ground fault phase of a non-effective ground system, for use in safe processing of a ground fault of a neutral point non-effective ground generator or distribution network. Non-effective ground system side windings of a transformer are equipped with a plurality of shunting taps. When a single-phase ground fault occurs, the shunting tap of the fault phase winding is selected to be short-circuited to ground directly or through an impedance to reduce the fault phase voltage to ensure that the fault point voltage is less than the continuous burning voltage of a ground arc to meet a long-term non-stop safe operation requirements. The proposed method can eliminate the instantaneous single-phase ground fault, suppress the permanent single-phase ground fault current, and limit the rising amplitude of non-fault phase voltage and the risk of non-fault phase insulation breakdown.