Abstract: According to arc voltage of CO₂ are welding characteristic, the feasibility of application wavelet transform theory to the detection of short-circuit signal in CO₂ arc welding and putting signal of short circuit control is tested, and frequency spectrum of true short circuit, false short circuit and noise are also analyzed. The mechanism of removing false short-circuit signal and noise signal by wavelet transform is analyzed by theory analysis and mathematics formula deduction. Different wavelet basic wave is used to analyzed arc voltage dispersed signal by Wavelet Toolbox in Matlab, finally feasible set of wavelet filters is achieved, and short circuit signal is detected in real time by program in DSP.