Many of single-core power cable insulation fault and metal sheath is concerned, only the simplified structure model of cable guide core cannot protect layer related to the fault location. Based on the distributed parameter model, a new fault location method considering the cable metal sheath is proposed. Firstly, Based on the distributed parameter theory, the equivalent distributed parameter circuit of fault cable with metal sheath is analyzed, and the voltage and current equations are established; Then, the unknown parameters in the voltage and current equations are solved by boundary conditions to obtain the voltage and current values along the line; Finally, the fault distance is obtained by constructing the iterative search of the fault distance equation. This method transforms the complex phase network into the independent sequence network, which makes the algorithm simple and effective. A large number of simulation results show that this algorithm can achieve accurate ranging of sheath fault (sheath to ground fault, core-sheath fault and core-sheath to ground fault), the error of ranging is basically less than 1.5%, and the positioning result is not affected by the fault location, fault type and transition resistance.