Fault line selection is difficult in isolated neutral system． A novel fault line selection scheme based on reactive current is proposed． After single － phase short circuit faults occur，the current change of fault phase in each line is mainly composed of capacitive current，and the current is reactive current． For fault phase，the reactive current change of fault line is larger than that of normal line． On this basis，the novel fault line selection scheme is proposed． A isolated neutral system model is built in PSCAD to research the reliability of the proposed scheme． The type of transmission line and grounding resistance are considered in simulation． Simulation results show that the proposed scheme can select the fault line with a high reliability．