Microstructure characterization and hardening behavior of a new designed Ti-12.1Mo-1Fe alloy during solution and aging treatment was investigated in the present study by OM, Vickers hardness. The results showed that the beta transus temperature of new Ti-12.1Mo-1Fe alloy was about 780°C. Further observation of ω phase should be performed by TEM later. It is also found that ω phase played a more important role than α phase in hardening. The hardening due to ω phase can lead to a high hardness about 470 Hv but the coarse α phases result in a hardness below 300 Hv.