The utility model aims to provide an arc ignition method of a plasma torch, and the method is suitable for arc ignition of a high-power and long plasma torch. The method is to connect at least two arc ignition circuits and a plasma power supply in parallel and then connect them to a plasma torch, start the arc ignition circuits after the plasma power supply supplies power to the plasma torch, and break down adjacent electrodes of the plasma torch sequentially from the first level, wherein the generated electric arcs are blown to the center area of the torch by airflow and are connected to form a longer arc. A principle employed in the method is to use charging and discharging characteristics of a pulse capacitor and to ignite an arc of a torch successfully by adopting the method of stepwise arc ignition.