A novel method of identifying fault line for single phase-to-earth fault in non-direct earth neutral system based on two-phase-current transformation（TPCT） is presented. TPCT is an algorithm that the currents of phase-a， -b and -c of each line add their leading current of phase-b， -c and -a that is turned 60 degree clockwise， respectively. The criterion of faulted-line identification is that the three-phase currents by TPCT of healthy line are equal while the three-phase currents by TPCT of faulted line are different， which has been proved theoretically. Computer simulation shows that the method of the proposed fault-line identification is not affected by fault resistance and load flow and can identify fault line correctly when a single phase to earth fault occurs in non-direct earth neutral system.