In the MV cable network, it is easy to have phase-to-ground faults, of which the ratio of arc grounding faults is high. What’s more, the process of it is complex and difficult to simulate. As a result, a new arc model for the small current neutral grounding mode is put forward. This paper studies the existing simplified arc models and simulates the arc models with Matlab. On this basis and in the background of MV cable network with the small current neutral grounding mode, the parameters of the models are improved. Then the voltage and current characteristics of the arc model are got. The model is verified with Matlab. Compared with realistic physical quantities, it can be proved that the improved arc model is applicable. The result affirms that this model is closer to the reality. It is an important technical basis for the study of the next step of cable network fault analysis.