Abstract: Aiming at some of deficiencies in the control system with analogous control technology and single-chip control technology,such as poor flexibility,control precision and reliability,a control system based on a digital signal controller(DSC) and micro control unit(MCU) for pulsed metal inert gas(MIG) arc welding power source is designed,and the hardware circuit and software flow chart of the system are presented.In the system,DSC with the variable parameter PI control algorithm controls the arc voltage and welding current,and the parameters of PI controller are determined by an expert system in MCU.The real-time kernel of the μC/OS-Ⅱis reduced and ported in MCU,and multiple tasks including an expert system are designed.The experimental results show that the control system based on DSC and MCU for pulsed MIG arc welding power source has the advantages of quicker response,better reliability and more stable arc length.