Abstract: A-MAG welding process was proposed, by which welded joints of high quality can be obtained. Arc morphology and weld pool flowing of A-MAG welding are observed and analyzed. In which the flow of molten pool was studied by using the tungsten particle tracer method. The test results show that the A-MAG welding arc is shrinking. The weld pool is more concentrated, the flow direction of liquid metal in the molten pool is from the periphery to the centre and the flow is more orderly. The change of the fluid flow in the molten pool is main factor of increased penetration.