Abstract: The single-phase arc grounding faults are common in isolated neutral distribution network, it is necessary to model and analyze its nonlinear characteristics in a proper way. The traditional methods rely on the simulation analysis of the arc black box model which is difficult to quantify the effects of arc non-linearity on fault transient characteristics. In order to solve this problem, this paper follows the idea of simplifying the arc model by retaining main features of the middle and low frequency of the arc, and proposes a Multi-odd frequency voltage source equivalent arc model which is more suitable for fault transient and steady state analysis. Then, combined with the transient equivalent circuit of isolated neutral distribution network, analytical expression of transient current in arc grounding faults under different fault resistances is quantitatively calculated, and the harmonic characteristics of the stable current of the fault are analyzed. The effectiveness of the new method is verified by simulation and experiment data. It provides a theoretical basis for subsequent research on arc grounding faults protection under different neutral grounding modes.