The invention provides an anti-viscin thread control method comprising the following the steps: feeding a solder wire doped with solder agent; carrying out constant voltage control according to a voltage setting signal (Er), thus outputting a welding voltage (Vw) and a welding current (Iw), and carrying out welding; if a welding start signal (St) is changed into a stop instruction, than the voltage setting signal (Er) is switched into an anti-viscin thread voltage setting value (Ear), thus stop welding. The anti-viscin thread voltage setting value (Ear) is set in vibration waveform, so the welding current (Iw) is set to vibration waveforms of triangle shape or sine wave shape, and the anti-viscin thread voltage setting value (Ear) is set to prevent short circuit in an anti-viscin thread control period (Ta); welding agent in the solder wire can be gasified so as to prevent slags from attaching to the front end of the solder wire. The solder wire with solder agent is used for arc welding so as to prevent slags from attaching to the front end of the solder wire, thus providing better arcing property.

The invention provides a start welding method for two-wire welding, wherein a welding line with enough bonding strength is formed after welding starts. Electric arc (2A) is generated from a wire (WA) as a wire (WB) is fed to the wire (WA) from back along the welding direction, which comprises a step of welding by electric arc (2A, 2B) and a step of welding only by electric (2A) through quenching the electric arc (2B). Enough heat is transferred to welding base metal (P) after welding starts so that enough width is provided at the beginning end of the welding line (Wp).