Abstract: This study develops a new high-speed rotating arc system to weld narrow gap joints.In this system,an electrode wire passes through the hollow axis of motor and then stretches out from an eccentric nozzle.The hollow-axis motor drives the offset nozzle and rotates the arc on the tip of wire at high speed,so as to ensure enough penetration into the sidewalls in narrow gap welding.Welding experimental results show that the rotating arc system can stably and reliably operate at different rotation frequencies and diameters,this process obviously improved the penetrations into sidewalls and bottom-side of bead,and simultaneously raised the burn-off rate of electrode wire.