Abstract: Based on the result of a comparative test study on AC square wave power source parameters, it is identified that the weld metal deposition rate in SAW process is more effectively controlled by adjustment of the duty cycle wave form parameters than by that of the offset wave form parameters.And further experiment result shows that the duty cycle parameters of the power source wave form have greater effect on heat input of the welding process, and it is beneficial for enhancement of the low-temperature impact toughness of the weld joint in case of using smaller duty cycle during multi-wire SAW process,