This paper presents a method to simulate the current and voltage of an electric arc initiated at the contact's opening in a contactor. Based on a simplified model of the electric arc and also on the dynamics of the contacts during the opening, this method allows to simulate the arc ignition as well as the arc extinction. This study is based on the hypothesis that the arc dynamic is much faster than the opening speed. This hypothesis allows us to use a static arc equation. The arc is described as a nonlinear resistance, which is dependant of the gap between the contacts. The parameters of the gap's equation are approximated by an analysis of the video obtained with a high speed camera during the opening of the contactor. The parameters of this arc's model are approximated by experimental tests on a DC contactor with AgSnO2 contacts. A fitting method is developed to minimize the error introduced due to the non-linearity when the static arc parameters are fitted to the static arc equation. Simulation results are compared with experimental data to demonstrate the validity of the suggested method.