Abstract: In order to effectively control MIG welding arc and droplet transfer and improve welding quality, the magnetron MIG welding droplet transition experiments under certain reasonable welding process parameters and excitation parameters were conducted. In the experiment, with the help of high-speed photographers, the variation patterns of MIG welding arc and melting droplets were collected under different directions of external magnetic fields. The results show that under different excitation currents, with the change of the magnetic field direction, the shape and movement of the arc and droplet change. Compared to the absence of an external magnetic field, the arc shape changes into "bell shaped", and the droplet changes from spherical to ellipsoidal. When the magnetic field direction is downward, the arc rotates clockwise around the axis of the welding wire, and the droplet rotates counterclockwise around the axis of the welding wire; when the magnetic field direction is upward, the arc rotates counterclockwise around the axis of the welding wire, while the droplet rotates clockwise around the axis of the welding wire.