The plasma-MIG welding torch was developed. 5A06 aluminum alloys with V-grooves were welded in a single pass in the plasma-MIG welding process and the joints were examined by X-ray diffractometry analysis and mechanical tests. The orthogonal experimental design was used to study the influence of plasma-MIG welding parameters on the aluminum weld porosity. The mixed orthogonal matrix L16(44×23) and analysis of variance (ANOVA) technique were employed to optimize the welding parameters. The experimental results indicate that the effect of plasma gas flow rate is dominant, the secondary factors are MIG welding voltage, welding speed, wire feed rate and plasma current in turn. Confirmation experiments were conducted under optimum conditions and there was almost no porosity in the welded joints, thus good mechanical performance joints were obtained.