The invention relates to a distance protection method and device for a phase-to-phase grounding fault. When a phase-to-phase grounding fault occurs in the oscillation process of a power system, and the impedance element action condition of the fault phase is satisfied, and the impedance element action condition of the non-fault phase is not satisfied, and the fault phase is selected as two-phase or three-phase, the grounding distance protection is opened. When phase-to-phase grounding fault occurs in weak feed system, impedance element action condition of fault phase is satisfied, impedance element action condition of non-fault phase is not satisfied, sudden change voltage selects two-phase fault, phase-to-phase grounding fault is removed by open grounding distance protection at this time.By modifying the action logic of the grounding distance protection in the program of the line protection device, the invention realizes that the grounding fault between the phases of the gate is cutoff by the action of the grounding distance. Whether the result of phase selection is two-phase fault or three-phase fault, it can ensure the effective removal of the phase-to-phase fault in the oscillating or weakly fed system.