Abstract: 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's reliability and stability.CO₂ welding process control software was deueloped based on μ C/OS-Ⅱ.The software development included the structure analysis of μ C/OS-Ⅱ,the migration of μ C/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.