The effects of Yb content on the microstructures and mechanical properties of 2519A aluminum alloy plate were investigated by means of tensile test,optical microscopy,transmission electron microscopy,scanning electron microscopy and X-ray diffractometer.The results show that addition of 0.17% (mass fraction) Yb increases the density of θ’ particles of the 2519A alloy plate and reduces the coarsening speed rate of θ’ phase at 300 ℃.Therefore,tensile strength is enhanced from 483.2 MPa to 501.0 MPa at room temperature and is improved from 139.5 MPa to 169.4 MPa at 300 ℃.The results also show that with the addition of 0.30% (mass fraction) Yb,the mechanical properties increase at 300 ℃ and decrease at room temperature.With Yb additions,the Al7.4Cu9.6Yb2 phase is found whilst the segregated phases of as-cast alloys along grain boundaries become discontinuous,thin and spheroidized. The effects of Yb content on the microstructures and mechanical properties of 2519A aluminum alloy plates were investigated by means of tensile test, optical microscopy, transmission electron microscopy, scanning electron microscopy and X-ray diffractometer. The results show that the addition of 0.17% (mass fractional) Yb increases the density of θ ’particles of the 2519A alloy plate and reduces the coarsening rate of θ’ phase at 300 ° C. The Tensile, tensile strength is enhanced from 483.2 MPa to 501.0 MPa at room temperature and is improved from 139.5 MPa to 169.4 MPa at 300 ° C. The results also show that with the addition of 0.30% (mass fraction) Yb, the mechanical properties increase at 300 ° C and decrease at room temperature. Whith Yb additions, the Al7.4Cu9.6Yb2 phase is found whilst the segregated phases of as-cast alloys along grain boundaries become discontinuous, thin and spheroidized.