The TIG welding process of ZL114A aluminum alloy that modified by Al-Sr master alloy was obtained by selecting welding vice and wire with different states and thicknesses. The chemical composition of the material was determined by inductively coupled method, and the effect of vacuum dehydrogenation on microstructure and mechanical properties nearby welding region were analyzed by Electronic hydrogen measuring instrument, OM, SEM, EDS, TEM and Universal testing machine. The results show that the hydrogen content decreases from 0.64×10_-6 to 0.26×10_-6, accompanying with the number of bubbles within 24mm and 12mm thickness reduce 71.4% and 60% individually, the diameter decrease from 2.3mm and 1.8mm to 1.4mm and 1.2mm, together with a reduced surface density by 77.7% and 81.8% after the vacuum dehydrogenation process. The morphology of silicon phase that distribute nearby grain boundaries transforms from needle-like to spherical, the particle size reduces from 106μm to 12μm, the average tensile strength, yield strength, elongation and reduction of area of 12mm thickness are 364MPa, 332MPa, 9.8% and 14.2%. The microstructure under T6 state mainly contains primary α-Al, primary and eutectic Si phase and Mg₂Si aging phase, the diameter of brittle Si particle is 4μm, Mg₂Si aging phase shows a rod-like morphology and the aspect ratio is 15.2, the shape of dimple changes from elliptical to spherical and the fracture mechanism evolves from intergranular frcture to dimple rupture after vacuum dehydrogenation.