The microstructure evolution and mechanical properties of Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe alloy after single and duplex aging treatment were studied. The Single aging temperature was 550℃, the duplex aging was pre-aged at 400 ℃ then re-aged at 550℃. The results showed that when the alloy pre-aged at 400℃, the ω phase was precipitated. As the pre-aging time prolonged, the ω phase finally changed to the α phase. Duplex aging was effective to yield the α phase fine dispersion, and the pre precipitated isothermal ω phase provided more uniform nucleation position for precipitation of α phase than single aging so as to improve the alloy tensile strengthen greatly. During pre aging, the isothermal ω phase could precipitate sufficiently so as to provide more advantageous nucleation position to precipitate very fine α phase of acicular style, and the strengthening effect was the same with that of duplex aging.