Abstract: Infuence of welding parameters on weld bead formation in high-spin-arc narrow gap MAG is investigated by utility of flat characteristic power.Experiment results show that spin arc can improve bead formation by distributing arc heat properly, while influence of spin frequency on melting rate is limited.Increasing spin frequency and reducing CO₂ content in the shielding gas can improve sidewall penetrationg and bead formation, but it may also lead to short circuit of the arc with sidewall and deterioration of bead formation, even lack of fusion.The spin frequency should be below 50 Hz when gap is less than 10 mm.Droplet transter manner will not be affected by welding speed, but a lower welding speed can get a bigger surface concavity.