Abstract: The effects of heat treatment system on microstructure and properties of TC11 titanium alloy were investigated.The results showed that with rising of temperature at air cooling condition,β phase volume of TC11titanium alloy increase,fraction of α phase decreases while the volume increase.When the temperature exceeds 1020℃,microstructure morphology of the alloy changes to fine acicular martensite microstructure.As the temperature continues to rise,α phase completely disappeared and further changes to widmanstatten and lamellar microstructure.The best mechanical properties of TC11 alloy are achieved after heat treating under a condition of 950℃/2h/AC+530℃/8h/AC,those are R_m 1050-1100 MPa,R_P0.2 950-1000 MPa,A 10%-16%,Z 30%-35%.