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In general, metastable β-Ti-alloys exhibit low ductility at room temperature, which restricts its workability and critical applications. Here, we report a hierarchical microstructure tailoring strategy to achieve an excellent strength-ductility combination in Ti-4Al-5Mo-5V-5Cr-1Nb (Ti-45551) alloy. It was revealed that high density deformation twinning can be successfully introduced in primary α particles of Ti-45551 alloy through warm dynamic plastic deformation (DPD). After warm DPD process, the hierarchical microstructure was constructed in Ti-45551 alloy, including equiaxed primary α particles with high density deformation twins, β-phase matrix and finely dispersed nanoscale secondary α lamellas. Uniaxial tensile experiments have revealed that Ti-45551 alloy exhibited enhanced strength-ductility synergy with hierarchical microstructure at room temperature. This excellent combination of strength and ductility is derived from high twin density in in primary α particles and unique hierarchical microstructure. Also, this study demonstrates a feasible and low-cost route to design high performance Ti alloy.