A　variable　polarity　pulsed　metal　inert-gas　control　system,　which　adopt　double　inverter　technology　using　isolated　gate　bipolar　transistor,　was　developed　based　on　TMS320F2812　digital　signal　processing　chip.　The　constant　current　inner　loop　is　fulfilled　in　the　first　stage　inverter,　and　the　constant　voltage　outer　loop　is　performed　in　the　second　stage　inverter.　By　using　proportional　integral　modulation,　I/O　port　and　D/A　converter,　and　the　output　parameters　of　welding　can　be　easily　controlled　with　high　precision.　At　the　same　time,　the　welding　device　has　lower　complexity.　Moreover,　the　welding　parameters　can　be　regulated　contemporary　and　output　current　of　variable　polarity　pulsed　welding　can　be　exactly　controlled.