Abstract: 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.