Intermittent arc grounding fault frequently occurs in non-solidly earthed networks. Establishing an accurate arc model is the basis for analysis of fault characteristics. Firstly, an improved cybernetic arc model is introduced in this paper, which can effectively demonstrate arc process in different situations through controlling the arc length. Then, it is applied to simulation analysis of intermittent arc grounding fault. Arc extinction and reignition criteria are proposed by comparing stable ignition voltage, air withstand voltage and system recovery voltage in diverse conditions. Finally, a typical simulation model of 10 kV distribution network is built via PSCAD. Impacts of different arc model parameters on fault characteristics are analyzed. Simulation and measurement results indicate the validity of the arc model and the feasibility of the proposed criteria.