Effects of solution treatment, single aging treatment, and duplex aging treatment on the microstructure and mechanical property of Ti-4Al-5Mo-6Cr-5V-1Nb alloy are studied. After the solution treatment at 820 ℃ for 0.5 h, α phase completely dissolved. The hardness of single/ duplex aging treated alloys both increase at the beginning and then decrease. The alloy duplex aging treated at 300 ℃ for 8 h and 500 ℃ for 8 h processes the peak-aging hardness of 458 HV, ultimate tensile strength (UTS) of 1462 MPa and elongation of 3.4%, whose UTS is 6% higher than original alloy and even higher than single aging treated alloy. The calculation of interface energy indicates that ω phase can promote the precipitation of α phase and the refinement of α lath by decreasing the nucleation resistance of α phase by 50%, thus increasing the hardness, strength, and elongation of alloys.