As　the　development　of　digital　welding　power　source,　the　hardware　and　software　of　its　control　system　is　becoming　more　and　more　complicated.　It　is　necessary　to　apply　real　time　operating　system　in　welding　process　control　to　assure　the　welding　power　source　reliability　and　stability.　CO2　welding　process　control　software　was　developed　based　on　μC/OS-II.　The　software　development　included　the　structure　analysis　of　μC/OS-II,　the　migration　of　μC/OS-II　on　MSP430F449,　the　development　of　task　code　and　the　response　time　test　of　short　arc　interrupt.　The　welding　process　showed　that　the　control　software　is　stable　and　reliable,　and　its　real　time　response　ability　meets　the　requirements　of　CO2　welding　process.