Due to the high stress, relative low density and excellent resistance of radiation, Zr-based alloys have become promising structural materials used in the space environment. The relationship between microstructure and mechanical properties is the key issue for designing Zr-based alloy in different alloy systems and has attracted extensive research interests. The microstructures could be adjusted by different processes of heat treatment and thus realizing the optimization of mechanical properties. In this work, the initial microstructure and mechanical properties of a high strength Zr₄₇Ti₄₅Al₅V₃ (mass fraction, %) alloy was investigated. The XRD results reveal that the initial Zr-based alloy is consisted of α (hcp) and β (bcc) phases. Transmission electron microscopy result shows that the lathy α phase homogenously distributed within the β phase matrix. Mechanical tests of this alloy show very high strength but limited plasticity. The tensile strength is 1648 MPa. However, the tensile elongation is only 0.8%. DSC trace indicates that the transition temperature of α phase to β phase is located between 560~750 ℃ that provides the possibility to adjust the microstructures through different processes of heat treatment. In order to optimize the mechanical properties, several different processes of heat treatment were conducted on this Zr-based alloy, and the relative volume fraction of α and β phase is successfully adjusted. According to the mechanical tests, the plasticity becomes larger as the amount of β phase increases with a slight decrease in strength. When the volume fraction of β phase is about 60%, the alloy exhibits the optimal mechanical performance with a tensile strength of 1398 MPa and an elongation of 3.1%.