This paper researches the influence of electrified railway on phase selector of digital protection device of 220 kV power transmission line in power system. According to the actual parameters of a regional power system, the electric locomotive model, the phase current difference superimposed phase selector model and the sequence component phase selector model are built in PSCAD. In PSCAD simulation, the phase current difference superimposed phase selector model can correctly select the fault phase in different conditions and the sequence component phase selector model can’t select the fault phase when the electric railway power is larger, so this paper reaches the conclusion that electrified railway on the phase current difference superimposed phase selector has little effect. It provides principle for installation the phase selection element in the electric railway transportation of heavy task area.