Abstract: The high-speed camera and electric signal acquisition system were used to record the current and voltage waveforms and metal transfer process in the double-wire welding of 5083 aluminum alloy under four synergy modes of Fronius CMT TWIN equipment. The characteristics of current and voltage waveform,the variation of arc length and the metal transfer mode were analyzed. The results show that the pulse time of the front and rear wires are consistent in the double-pulse mode,the pulse frequency is mainly determined by the time of the dimension arc stage,and the metal transfer mode is injection. In the double CMT mode,the front wire waveform is consist of pulsed stage with longer time and CMT stage with shorter time,the metal transfer modes are jet during pulsed stage and short circuiting during CMT stage,the rear wire is CMT mode,the metal transfer is mainly short circuiting. For hybrid modes of pulse + CMT and CMT + pulsed,the CMT waveform does not change,but the current and voltage of the pulse waveform are fluctuation. The variety of current and voltage and metal transfer are important to the change of arc length. In the front wire of pulse mode,the weld penetration and width are large,while in the rear wire of CMT mode,the reinforcement is high.