Abstract: The electric signals of short circuiting transfer in CO₂ welding were analysed with Fourier series, which consist of many elementary waves with different frequency, including the inherent high frequency elementary waves and interfere signals of high frequency besides low frequency elementary waves.The wavelet filtering with adjustable threshold was applied to study the signals of both general and waveform controlling short circuiting transfer, which indicates the importance of a suitable waveform data processing method to short circuiting transfer in CO₂ welding.