In the non-effectively earthed distribution network，the fault location method based on transient current similarity between upstream and downstream fault points lacks rigorous theoretical proof and suffers definite blind area in principle，which may lead to the failure of location.A transient model applied to single-phase earth fault location is built，and the relationship of transient current's dominant resonant frequency between upstream and downstream fault points is analyzed.A novel fault location method based on transient current comparison which synthesizes the similarity and polarity relationship of transient current is proposed.The fault is located in the section on whose two sides the transient currents are similar but have opposite polarity，or located in the first section with dissimilar transient currents on the two sides.In the resonant earthed system，the consistency of polarity relationship between power frequency current and transient current at detecting points can exclude the effect of the anti-polarity current transformer.This method can eliminate the blind location area，while improving the reliability and adaptability of the transient-fault-location principle.The effectiveness of this method is verified by simulation and field data.