Abstract: The wire arc additive manufacturing technology (WAAM) based on cold metal transfer was used to prepare WAAM 2319 aluminum alloys by 2319 aluminum alloy wires with different yttrium (Y) content, and the effect of Y content on the microstructure and mechanical properties of WAAM 2139 alloy were investigated. The results show that the grain of as-deposited WAAM 2319 aluminum alloy is obviously refined after adding Y, which has the effects of fine grain strengthening and second phase strengthening, which affected the formation amount of the secondary precipitates θ' in the aging process indirectly. Meanwhile, the size and distribution of pore defects in WAAM 2319 aluminum alloy are not significantly affected with the addition of Y. With the increase of Y content, the degree of segregation of Y-containing compounds at the grain intersection during the solidification process of the alloy increases, which reduces the component undercooling, and resulting in the grain size of WAAM 2319 aluminum alloy decreases and then increases, the tensile strength and yield strength increase and then decrease, and the elongation decreases gradually. When the Y content reaches 0.15%, WAAM 2319 aluminum alloy reaches the optimal value of mechanical properties with tensile strength of 484 MPa, yield strength of 348 MPa and elongation of 10.5%.