Abstract: Wire arc additive manufacturing process based on argon tungsten arc welding (GT-WAAM) was carried out on 6 mm-thickness Ti6Al4V alloy base metal with 1.2 mm-diameter filler wire as material, and CO₂ was uses for interlayer cooling to obtain uniform deposition structure. By analyzing characteristics of thermal cycle, deposition morphology, hardness distribution and mechanical properties of welding process, quality evaluation of deposition structure was obtained. The results showed that increasing cooling rate could refine grains of deposition structure and obtain acicular α′ phase, thus improving hardness and tensile strength of material. In deposition structure, heat accumulation effect caused by the increase of deposition height made it possible for C and O elements in cooling gas to have a potential chemical reaction with deposition metal. Using interlayer cooling to control interlayer temperature could effectively improve quality of deposition structure and increase manufacturing efficiency by more than 80%.