Abstract: It is found that in the plasma-MIG hybrid welding of aluminum alloy, when the plasma arc welding current is 130 A and the MIG welding current is 180 A (base current is 95 A), the resistance of MIG arc near the plasma arc in the base current time is small, and the voltage of MIG arc in the hybrid welding is lower than that in the single MIG welding in the pulse base period, and the main ionization medium of the MIG arc biased towards the plasma arc is Ar. When the MIG welding current increases to 240 A (base current is 122 A), the above phenomenon disappears. Due to the thermal inertia of the welding arc, when the MIG arc is biased towards the plasma arc in the base current period, the MIG arc will still be biased towards the plasma arc in the pulse current rising stage and when the current has just reached the peak current, the MIG arc voltage in the hybrid welding is higher than that in the single MIG welding. When the MIG arc is biased towards plasma arc in hybrid welding, the stability of MIG arc decreases. With the increase of MIG welding current, the arc stability increases.