Abstract: According to algorithm a'trous and analysis of CO₂ arc voltage characteristic by Wavelet Toolbox in Matlab,the wavelet algorithm which is suitable for detection of short-circuit signal in practical CO₂ welding process is derived.Different wavelet basic waves are used to analyze the CO₂ arc voltage signal in Matlab,finally the db2 basic wave is selected and used in this algorithm in which the filter is stationary and the sampling signal is processed one by one by three-decomposition.To meet real-time requirements,the main program is developed in C++ and the assembly subroutine of wavelet detection is developed by the multiplier of DSP and the RPT instruction.As a result,it has a fast operation speed and improves the real time capability of detection.The calculation results of C++ program show the accuracy and the feasibility of this algorithm.Experiment results show that false short-circuit signal can be removed by the db2 basic wave and the short-circuit moment can be decteted in real time by this algorithm.