Abstract: A method to estimate CO₂ arc welding stability was proposed based on quantitative analysis of class frequency distribution of short-circuit time.Normal probability density function was applied in frequency distribution fitting,and the peak height of normal probability density function was obtained.With repeated times of fitting,a more reliable average of peak heights was calculated.The average served as an index to quantify the concentration degree of class frequency distribution.To test the effectiveness of the above method,an experiment on the stability of CO₂ arc welding was conducted,in which voltage and current signals in the typical arc welding processes were collected.The stability of the welding processes was firstly evaluated by the artificial approach.Then the new method proposed in this paper was adopted to calculate the quantitative index of stability in every arc welding process.After comparison,it was found that the results obtained by using the new method are consistent with those achieved by the artificial qualitative approach, which showed that the new method positively contributed to the objective evaluation of the stability of CO₂ arc welding processes.