Abstract: Variable polarity pulsed MIG welding of thin sheet aluminum alloy is realized by full bridge bidirectional high voltage arc stabilizing method, and the influences of voltage amplitude of high voltage arc stabilizing pulse, pulse duration, pulse triggering time and background current on cross zero stability are also investigated.When small background current crosses zero, the influence of arc stabilizing pulse voltage on cross zero stabilityis is more than that of background current.The rise rate of arc stabilizing pulse voltage which influences the cross zero stability has a critical span, in which the arc is unstable when arc current crosses zero. Estimating the cross zero stability of VP PMIG through calculating the rate of arc stabilizing pulse voltage, it can offer an efficacious and crediblewarranty to the reignition of the cross zero welding arc of aluminum alloy VP PMIG.