Abstract: A new heterogeneous twin-wire indirect arc additive manufacturing (TWIA-AM) method was proposed. The ER2319 wire and ER5356 wire were fed synchronously and Al-3.5Mg-1.7Cu alloy components were prepared. The microstructure and mechanical properties of the deposited Al-3.5Mg-1.7Cu alloy components were investigated. The results showed that the second phase composition of Al-3.5Mg-1.7Cu alloy was mainly Al, Mg and Cu, and consisted of α-Al and S (Al₂CuMg) phases. The grain morphology appeared as coarse columnar crystals at interlayer regions, and the center area of the layer is composed of equiaxed crystals and fine cellular crystals, and the layer center region was composed of equiaxed crystals and fine cellular crystals. The average micro-hardness of the sample is 73.7 HV with a periodic low hardness zone. The average tensile strength and elongation of the samples parallel to the building direction (BD direction) and perpendicular to the BD direction were 225, 235 MPa, 9.0% and 13.0%, respectively, exhibiting anisotropic mechanical properties. The fracture morphology exhibited the characteristics of typical plastic fracture.