Abstract: Welding electrical parameters (arc voltage and welding current) include abundant information of welding procedure. This paper collects instantaneous value of arc voltage for underwater wet manual arc welding at different welding conditions, taking different depth and welding electrode for instance. And then,the instantaneous value of voltage was processed statistically. The process stability of underwater wet manual arc welding was analyzed visually and evaluated quantitatively based on standard deviation (σ_U),the combination of frequency distribution of the D-value (H) between instantaneous value and mean value of arc voltage with stability exponential (W). The result shows that the stability of different welding process could be well identified,which is very theoretically meaningful as giving a new method for stability control for underwater welding process.