Abstract: Unifying control of carbon dioxide are welding machine adjusts the welding current and voltage by turning one-knob only, chaff.ging current directily and corresponding arc voltage indirectly, to obtain the optimum match and ultimate short-circuit transfer frequency.However, the transfer process of carbon dioxide short-circuit arc welding is difficult to be described in accurate model, and the unifying control method by traditional controlling theory is not realyy one-knob adjustment. Aimed at this issue, the authors present an arc voltage self-optimizing fuzzy control system of carbon dioxide short-circuinting transfer welding, its key component is a 16 bit 80C196KC single chip microcomputer, and the funzzy control is realized by software programming. to aim at the optimum result of ultimate frequency of short-circuiting transfer and according to the only selected value of welding current, the arc voltage can the automatically adjusted to the optimum value to really realize the unifying control of oneknob adjustment.