Abstract: A self-designed microcomputer control system for pulsed metal inert-gas (MIG) welding power source,the selection of proportional-integral-differential (PID) algorithms,and the optimization stratege of system conntrol software were introduod.To solve the conflict between proportional-integral (PI) control and real time display of welding parameters in MIG welding,the working Timing Diagram of serial display component MAX 7219 was analyzed,and the data and command transfer ways of it and the way to optimize PID control algorithms on the premise of avoiding system damping were improved.PI control time is only 80 μs and one bit digital display was refreshed every 200 times (about 16 ms).The display flash problem was solved.The result showed that the optimized program run very fast,responded very quick,and was very accurate,and the welding proass was very stable.