The accurate identification of the faulty phase is of great importance for active interference arc suppression device. When mis-selection occurs, more serious inter-phase fault occurs. In order to improve the accuracy of fault phase selection, method of phase selection using additional resistance of neutral point is presented. The method calculates the parameters of ground in real time by switching in/off the additional resistance on the neutral point, and the equivalent impedance of the network can be estimated. Then the fault phase can be identified by using the difference of parameters between normal and fault states. Simulation results show that this method performed better than the traditional phase voltage amplitude comparison method. The accuracy for faulty phase selection is high even under arcing or high resistance grounding fault scenarios.