Abstract: The experimental characteristics of pulsed alternating current plasma arc (PA) - gas tungsten arc (GTA) double-sided arc welding process on LY12CZ aluminum alloy were analyzed in detail. Experimental results showed that, compared with regular GTAW and PAW process, the pulse AC PA-GTA double-sided arc welding process can remarkably increase the weld penetration, minish heat distortion and improve the weld efficiency. Plentiful experiments with multi-nozzle and single nozzle showed that double arc on the plasma arc torch can be prevented effectively with multi-nozzle, and deeper penetration can be reached with single nozzle. Arc cleaning action effect falls after the keyhole was established during keyhole pulsed AC PA-GTA double-sided arc welding process on aluminum alloy, which influences, the shape and quality of the weld.