Abstract: A microcomputer experimental system has been made for the control of current wave form during the short circuiting metal transfer of CO₂ welding process. This system can produce a negative pulse of current at any moment of the short circuit transfer. The result of welding tests shows that this system can reduce the welding spatter effectively when the program parameters t₀、△t and △I are properly chosen. The system has many practical prospects in welding production applications. This paper mainly introduces the electrical circuits and the control program of the system as well as the effect of the parameters of the circuits and the program on the wave form and the amplitude of the negative current pulse.