Abstract: AC fault arc is a serious threat to the safe and stable operation of electrical equipment,and can easily cause fire. In order to study the influence of different clearance distances on the various physical fields of AC fault arc,a magnetohydrodynamic model is established based on an analysis of energy conversion process of AC fault arc.And a two-dimensional axisymmetric model is established with COMSOL Multiphysics software,to simulate the complex AC arc.The changes and relations of terminal current,voltage,temperature field and magnetic field when the electrode distance is 2 mm are analyzed,and the influence of different electrode distances on the distribution of voltage and current and arc temperature at AC arc terminal is studied,which provides an important reference for the design of AC fault arc extinguishing device.