The invention relates to a dual-gun type arc variable plasma flying ash treatment apparatus and method. The treatment apparatus comprises a feeding port and an exhaust port formed in the upper part ofthe shell, a discharge port formed in the bottom of the shell, and two plasma guns which are arranged on the upper part of a furnace body in a run-through manner, wherein the interior of the shell isin a micro negative pressure state; a baffle is arranged on the discharge port; plasma arc spraying ports of the plasma guns are positioned above flying ash mixed with quartz sand, and the flying ashis positioned at the internal bottom of the furnace body; the plasma arc melts flying ash into a molten state; the electrodes of the two plasma guns can perform switching among non-transfer arc, conjunct arc and transfer arc; the two plasma guns are connected with a gas supply station and a power supply separately; and through the power supply, the polarities of the electrodes in the two plasma guns can be changed, so that transfer arc plasma can be generated between the two gun bodies, thereby facilitating reduction of thermal loss and prolonging the service lie of the electrode outside a spraying nozzle.