Three kinds of working modes including DC pulse TIG weld,DC TIG weld and DC manual weld. Excellent performance of arc starting, success probability of arc establishment is near to 100% under small current. According to the different requirement, the switch of the welding gun can be set up three kinds of control modes including short arc,long welding and electrical arc. According to the different purposes,adopting three kinds of pulse control modes including Iow frequency, middle fie quency and high frequency. Having fine protecting functions including overcurrent, overheating, undervoltage and scarcity of phase.