Abstract: Cable carbonization path is an important scenario of electrical fire. The cable insulation material forms a carbonization path after being ablated by fault arc. It may form a conductive circuit between cables or between cables and ground, which can easily lead to short circuit and electrical fire, and seriously threaten the safe and stable operation of power system. Researching the mechanism of cable carbonization path is an important issue concerned by the industry. Based on the working conditions of the experimental platform developed by the research group, this paper carries out simulation and experimental research on the carbonization process of cable insulation materials caused by fault arc. Through the thermogravimetric test, the kinetic model of thermal decomposition of cable insulating materials is established. And the neural network is used to extend the pyrolysis kinetics parameters to the high heating rate environment of the arc, which provides the basis of reaction mechanism and parameters for the simulation of cable carbonization path. On this basis, a circuit-arc-pyrolysis coupling simulation method is proposed for the first time, and a three-dimensional numerical model of cable carbonization path under AC fault arc is established. The development process of cable carbonization under the coupling action of arc heat and flow is calculated. In addition, the effects of pyrolysis kinetics parameters and pyrolysis gas velocity on fault arc and cable carbonization are discussed. The work of this paper lays a theoretical foundation for studying the mechanism of cable arc fault.