Abstract: On the basis of designing a longitudinal magnetic field generator with powerful engineering practicability and miniaturized structure, the longitudinal magnetic field is applied to streaming transfer MAG with the shielded gas of 98%Ar and 2%O₂.Magnetically induced rotating MAG welding process is put forward.At the meantime, the influence on arc shape and moving behavior, wire melting character, drop transfer mechanics, and weld formation of exciting current is studied.The shortage of deflecting weld for this new welding process is pointed out.The result shows that under the effect of the outer longitudinal magnetic field, all of arc and molten cone and liquid metal jet deflect from the wire axis and rotate with high speed.The larger of the exciting current, the faster of arc rotating angular velocity, the shorter of arc length, the faster of drop transfer frequency, the lower of welding current and the larger of wire melting coefficient.