Abstract: Based on the experimental time series of welding current produced by CO₂ welding with short-circuiting transfer under different arc voltages,gas flow rates and welding speeds,the approximate entropy of the welding current has been numerically evaluated by the implementation of Pincus's algorithm.The different effects of approximate entropy and droplet short-circuiting transfer frequency on the welding process stability are also analyzed.Experiments and numerical analysis demonstrate that approximate entropy reaches larger values when the welding processes approach more steady states under the condition of the three above-mentioned process experiments.The variation trend of the droplet short-circuiting transfer frequency is not always consistent with that of welding process stability.So approximate entropy characterizes the welding process stability more accurate than the droplet transfer frequency.