The effects of single cold rolling annealing, three times cold rolling annealing and subsequent aging on the microstructure and mechanical properties of self-designed metastable β titanium alloy Ti-7.46V-5Mo-3.13Cr-1Zr-3Al were investigated by optical microscope (OM), X-ray diffractometer (XRD), scanning electron microscope (SEM) and room temperature tensile tests. The results show that: compared with single cold rolling annealing, the grain size of the alloy after triple cold rolling annealing is finer, the strength and plasticity are improved, the yield strength reaches 815 MPa and the elongation is 27%. After single cold rolling annealing and aging treatment, the secondary α phase with fine and dispersion is precipitated, the yield strength of the alloy reaches 1280MPa, and the yield strength increases at first and then decreases with the increase of aging time, showing higher strength and lower elongation; However, the strength of the sample after triple cold rolling annealing and aging is slightly lower, but the plasticity is significantly improved, and it has a better match between strength and plasticity. Based on the comprehensive comparison of the experimental results, it can be determined that the alloy can achieve a good match of strength and plasticity after triple cold rolling annealing at 800℃/20min and aging at 500℃/10h, the tensile strength is 1380MPa and the elongation is 10.8%.