The present invention obtains an automatic mode switching of DC plasma torches through, which easily switches DC plasma torches to be run between a transmitting mode and a non-transmitting mode and put the switching device under the monitor and the control of a current sensor and a current level controller; the heat generated by the current passing through can be transferred by a non-combustible liquid driven by a pump and be cooled down through a heat exchanger; and, electric arcs is prevented from happening between two electrodes by the non-combustible liquid.