A waveform fuzzy logic control method used in CO2 gas metal arc welding was proposed in order to get stable arc length with constant current output characteristics. Working principle of the waveform control system was presented and designing procedures of a fuzzy logic controller were provided. Experiments with the above method were conducted. The results indicated that the proposed method works satisfactorily, giving rise to an excellent comprehensive technological performance. The performance includes a stable welding process, few spatters and a good bead formation.