Abstract: This paper focuses on understanding the mechanical properties,deformation,and failure mechanisms of Ti-4Al-6Mo-2V-5Cr-2Zr (wt.%) metastable β titanium alloy under different microstructures,through tensile tests at room temperature. Results of microstructural characterization show that the microstructure of the forged alloy consists of a single β-phase. After a solution plus aging treatment in the β phase region,the microstructure of Ti-4Al-6Mo-2V-5Cr-2Zr alloy mainly consists of secondary α-phase (αs) and residual β-phase,presenting a typical lamellar structure. After a solution plus aging treatment in the α+β phase region,the microstructure of Ti-4Al-6Mo-2V-5Cr-2Zr alloy mainly consists of nanoscale αs and microscale primary α-phase (αp) and grain boundary α (GB α),forming a typical layered nanostructure. The forged alloy has the lowest ultimate tensile strength (UTS) and the highest elongation (El) of 807 MPa and 23%,respectively. The lamellar-structured Ti-4Al-6Mo-2V-5Cr-2Zr alloy has the highest UTS and lowest El of 1235 MPa and 10.5%,respectively.