In order to locate the fault online by traveling wave without replacing the original electromagnetic current transformer in the GIS, using the 110 kV XLPE power cable as the prototype, the transient current propagation characteristics in the sheath cross-bonded cable are analyzed. The method using the sum of three sheath currents as fault location signal is proposed. The signal doesn’t change in the sheath-crossing point and sheath grounding point, and the main component of the signal is a stable modulus. A model of 110 kV power cable system is built by PSCAD/EMTDC to simulate various fault resistance and fault location. Using the wavelet transform modulus maxima to locate the arrival time of traveling wave, the result shows that the method is feasible and has higher accuracy.