Abstract: The regulation of ending progress in variant polarity plasma arc welding with keyhole was studied.The welding current,welding speed and the plasma gas flow rate were the most important parameters in the ending stage.The arc crater could be successfully filled by increasing wire feed speed,reducing ion gas flow rate as well as welding speed.The welding parameters in ending stage had their best ranges for material with different thickness.The weld mechanical properties of the joint at the end of the weld were not less than that at the middle of the weld.