Based　on　separability　of　plasma　arc,　the　twin-body　plasma　arc　was　established　as　the　wire　was　the　guided　electrode.　Combined　with　electrical　signals　and　droplet　transfer　behavior　of　different　welding　parameters,　the　droplet　transfer　behavior　under　different　bypass　modes　was　analyzed.　The　results　showed　that　as　the　bypass　mode　was　constant　current　mode,　the　droplet　achieved　steady　and　rapid　transition　as　the　bypass　current　increased,　the　transition　frequency　increased　as　the　wire　feed　speed　increased.　But　when　the　wire　feed　speed　was　too　fast,　the　wire　passed　through　the　plasma　arc　without　formatting　droplet.　With　the　change　of　the　bypass　current　and　wire　feed　speed,　the　bypass　voltage　and　the　plasma　arc　voltage　occurred　significant　fluctuations,　but　the　bypass　current　and　the　plasma　arc　current　remained　stable,　the　bypass　voltage　increased　as　the　plasma　voltage　dropped.　As　the　bypass　mode　was　constant　voltage　mode,　droplet　achieved　stable　and　rapid　transition　as　the　bypass　voltage　and　wire　feed　speed　increased,　losing　its　stability　as　the　overloaded　voltage　was　set.　With　the　change　of　the　bypass　voltage　and　wire　feed　speed,　the　bypass　current　was　increased　as　the　bypass　voltage　increased,　but　the　plasma　arc　voltage,　the　voltage　bypass,　the　bypass　current,　and　even　the　plasma　current　showed　significant　volatility.　©　2017,　Editorial　Board　of　Transactions　of　the　China　Welding　Institution,　Magazine　Agency　Welding.　All　right　reserved.