Al-6.3Cu alloy straight wall samples were produced using AC-GTAW process. The influence of heat input, environmental atmosphere, and wire feed speed on porosity characteristics of deposition samples were investigated. It is observed that heat input is the most important factor affecting the porosity defect. Gas pore counts and its diameter can be reduced with proper heat input. With lower heat input, the gas pores can be further reduced in argon environment and lower wire feed speed. The experimental results show that, in argon environment, with travel speed of 0.30m/min and wire feed speed of 2.0m/min, the gas pores can be controlled effectively.