Abstract: The direct diffusion bonding of TiAl alloy and the diffusion bonding of TiAl alloy with hydrogenated 0. 5%（ mass fraction） TC4 titanium alloy were carried out. SEM,EDS,XRD and shear strength test were employed to investigate on microstructure and properties of bonded joints. Effects of bonding temperature,bonding time and bonding pressure on the interface and mechanical properties of bonded joints were studied. The results showed that holes at the direct diffusion bonding interface of TiAl alloy completely disappeared at bonding parameters of 1473 K,60 min,30 MPa,and shear strength of bonded joints was up to 285 MPa. When hydrogenated 0. 5% TC4 titanium alloy was used as the intermediate layer in diffusion bonding of TiAl alloy at bonding parameters of 1 123 K,30 min,15 MPa,holes at the diffusion bonding interface disappeared,together with a certain thickness of the reaction layer generated,and shear strength of bonded joints was up to 290 MPa.The phase composition of fracture interface was mainly composed of brittle phases,such as TiAl,Ti₃Al,TiAl₂ and Ti₃Al₅. Compared with the direct diffusion bonding,the diffusion bonding parameters of TiAl alloy could be greatly reduced by using hydrogenated 0.5% TC4 alloy as intermediate layer in diffusion bonding of TiAl alloy.