Abstract: In view of the strong coupling among conductors of 10 kV three-core armored cable, and the difficulty of parameter calculation and fault type identification, a method of parameter calculation and fault identification of three-core armored cable is proposed. In this research, a technical scheme for calculating the impedance matrix of three-core cables using loop analysis method was first designed. The calculation accuracy advantage of this method was verified through experimental comparison. On this basis, the multi-conductor transmission line theory is innovatively combined with the loop analysis method to build a phase-mode transformation matrix model of the three-core cable, and the first end of the cable under normal operation and fault conditions is systematically derived. Input impedance characteristics. This research provides a new theoretical basis and calculation method for the impedance characteristics analysis of cable systems. Then, various fault types of the three-core cable are identified by combining the number of resonant points, the magnitude of the resonant amplitude and the change of the initial phase angle in the input impedance spectrum of the three-core cable. Finally, take the 10 kV ZR-YJLV22-3×240-8.7/15 three-core cable as an example, through the actual test to verify the effectiveness of the identification method.