Abstract: Four multi-layer single aluminum alloy beads using the same welding parameters were formed on substrates with four kinds of thickness by TIG arc. It is found that deposited metal width in stable region of different samples was basically unchanged. Based on this phenomenon, the experimental samples were designed using quadratic general rotary unitized design method and the model between process parameters (welding current, welding speed, wire feed speed and inter-layer temperature) and deposited metal width of stable region was established. The validation results show that the model has good prediction accuracy. Furthermore, it also reveals that the welding current, welding speed and inter-layer temperature were the main influential factors on deposited metal width. Among them, the welding current had the most influential effect, and then the welding speed and inter-layer temperature, successively. In addition, the welding speed and inter-layer temperature had interactive effects on deposited metal width.