Abstract: A new control method of welding current waveform was investigated to solve the problem of bad weld appearance and much spatter in high-speed CO₂ arc welding, which controlled the short circuit current and its rising rate in short circuit period, and adopted the two-step constant current method of big constant current and small constant current to adjust the arc energy in arc period. According to the control principle, the sy stem based on a single chip computer and the software of the waveform control were developed. The effect of waveform control parameters on weld appearance was analyzed, and the parameters were optimized.The results show that this system can precisely control the arc energy with the two-step constant current method, and obviously improves the performance of welding process, and meets the needs of high-speed CO₂ arc welding.