The arc grounding fault in the distribution network is highly possible, the dynamic characteristics of which play an important role in detecting arc faults. The Mayr and Cassie models are two classical models in the study of arc grounding faults in distribution networks, which are suitable for describing different physical properties of arc. In this paper, the transition function is established by using the arc current as a variable, and a Mayr-Cassie combinatorial model is constructed. The model considers both arc convection heat dissipation and radial conduction heat dissipation. The single-phase arcing fault model is built on the PSCAD / EMTP platform. The dynamic characteristics of arc voltage, current and resistance are analyzed. The model is further used in the fault analysis of a specific 10kV distribution network. The results show that the model can accurately reflect arc characteristics.