The microstructure control and corrosion resistance of aluminum alloys fabricated by wire and arc additive manufacturing（WAAM） are important issues that must be studied in engineering applications. The 5356 deposited part is produced by a CMT （cold metal transfer） system. The microstructure and hardness are characterized by metallurgical microscope， X-ray diffractometer （XRD）， scanning electron microscope （SEM） and micro-hardness tester， and the corrosion resistance behavior is studied by using electrochemical workstation， slow strain rate stress corrosion testing machine. The results show that the microstructure of 5356 WAAM aluminum alloy is composed of α-Al matrix and β（Al₃Mg₂） phase. The grains in the deposition layer are columnar crystals with an aspect ratio of ≤2， and the β（Al₃Mg₂） phase exists mainly as finely dispersed particles， while the grains in the interface layer are recrystallized equiaxed grains with smaller size， and the β（Al₃Mg₂） phase is predominantly distributed in large discontinuous blocks along the grain boundaries， with fewer fine granular β（Al₃Mg₂） phase within the grains， leading to a reduction in the matrix strengthening effect. The self-corrosion current density of the deposited layer is 23% of that of the interface layer， which may be caused by the content and morphology of β（Al₃Mg₂） phase. The stress corrosion sensitivity index at a slow strain rate of 5356 WAAM aluminum alloy is 0.57， and samples experience fracture and failure at the interface layer in both silicone oil and 3.5%NaCl solution medium. This is attributed to the lower strength at the interface layer matrix and shearing effect played by large intergranular β（Al₃Mg₂） phase in silicone oil inert medium， while the β（Al₃Mg₂） phase dissolves preferentially in the 3.5%NaCl aqueous solution， and intergranular corrosion propagation is accelerated under tensile stress.