The arc characteristics and droplet transfer behavior in plasma-GMAW-P hybrid welding were investigated. The effect of plasma arc current on GMAW-P arc shape and metal transfer was discussed. The results indicate that the plasma arc will change the electrical conductivity and stress state of GMAW arc to affect the morphology of GMAW arc and droplet transfer behavior. When the plasma arc current is small, the GMAW arc in the base current period basically burns along the wire axis, and the bell-shaped GMAW arc in the peak current period is compressed due to two opposite forces (the electromagnetic force generated by the plasma arc and the wire) in the welding direction. At this time, the drag force of plasma flow and its downward component increase, the droplet transition is promoted, and the detached time of droplet is shortened. When the plasma arc current reaches a certain value, the metal vapor in the atmosphere near the plasma arc increases, and the conductive path of the GMAW arc will be changed to bias the GMAW arc to the plasma arc. At this time, the downward component of the drag force of the plasma flow on the droplet decreases, the promotion of the droplet transition is weakened, and the detached time of droplet is increased.