A simulation model for the column behavior on the long gap free arcs in air was constructed. In this model, the current path of the arc column was assumed to be a string of many nodes separated by very short intervals. Concerning the operation of the nodes, we considered the continuous motion due to the Lorentz force and the instantaneous motion due to the partial shorting, and introduced two special parameters to control them. One parameter was used to control the velocity of the continuous motion of the arc column, while the other was used to control the occurrence frequency of the partial shorting on the arc column. To evaluate the validity of the constructed simulation model, the column behaviors on DC free arcs with currents of 100, 500 and 2000A respectively on a gap length of 1.6m were simulated with giving various values to two special parameters. Consequently, it was proved that the simulation results with certain suitable values on two special parameters showed similar column behaviors to the actual characteristics, and that the constructed simulation model was valid.