Abstract: Wire and Arc Additive Manufacturing(WAAM)technology features high deposition efficiency,low heat input,stable forming process,and excellent mechanical properties,offering broad application prospects in the direct forming of large-size metal components.The WAAM technique based on Cold Metal Transfer(CMT)was employed to form 5087 aluminum alloy,where the single-cladding and multi-layer forming process and dimensional control were studied,and the microstructure and tensile properties were analyzed.The results showed that the dimensional accuracy of single-cladding height and width is within 0.5mm.Metallographic examination of the samples revealed that the grain morphology exhibited columnar crystal characteristics.On the horizontal cross-section of the samples,grain sizes ranged from 10µm to 50µm,while on the vertical cross-section,they ranged from 50µm to 80µm.Within the grains,dendrites were present in a mixed state of dendritic and cellular.Tensile test results indicated that the maximum tensile strength of the samples ranged between 200MPa and 230MPa,the maximum yield strength ranged between 100MPa and 120MPa,and the elongation was between 6%and 12%.The porosity in the 5087 aluminum alloy adversely affected the tensile properties of the samples by WAAM.