Abstract: The study of inductor-disconnected-discharge (IDD) arc in an explosive environment is an effective means to solve the problem of intrinsically safe inductive circuit split-off discharge, which is of great significance to promotion and application of intrinsically electrical and electronic equipment. In the arcing process of the IDD based on the IEC safety spark test apparatus (IEC-SSTA), it is found that the inter-electrode voltage jumps quickly to the melting voltage, and then quickly rises to the minimum arc-building voltage. To reveal the arcing mechanism and the generating mechanism of the cathodic sheath, an electronic drift diffusion model and a non-electron component heavy material transport model are established to obtain the evolution laws of various particles, inter-electrode potential, electron temperature, space charge and active radicals in the CH₄-Air arcing progress.Numerical simulation results show that the density of positive charge in space increases, which causes electric field distortion to form a cathode sheath layer, and active radicals produced by arcing process, such as N₂, O₂, —CH₃, —CH₂, and H, can facilitate arc formation. The differential reduction of the pole spacing cannot maintain arc discharge until the additional voltage is less than 15 V, and the pole spacing is close to the average free range or electron collision ionization of CH₄−Air.