An arc model based on the N S equations modified by adding an energy source term to take account of the arc is developed and solved using Taylor galerkin FEM in the present paper. The numerical method is applied to the simulation of the breaking process of a puffer type GCB. Moving boundary conditions of the arc chamber during operation is taken into account. Numerical predictions of the temperature profiles and pressure distribution at different strokes as well as the arc voltage are presented. The numerical results agree well with the experiment.