Abstract: The characteristic of power cable defects and fault types are analyzed in urban power grid construction, and a research method for characteristics of power cables is put forward based on head end impedance spectrum. At the same time, the cable simulation models with different defects and fault types are built, and the results are compared with the results of actual test. The results show that the cable defect will cause the input impedance spectrum shifts and the resonant frequency point change. Open circuit fault and short circuit fault will increase the oscillation period of input impedance spectrum. The simulation curves are basically consistent with the test results.