The thermal deformation tests of diffusion-bonded region of TC4 titanium alloy was carried out at deformation temperatures of 920,950,980,1010 ℃ and strain rates of 0.01, 0.1, 1,10 s-1. The effects of deformation temperatures and strain rates on flow stress and microstructure of diffusion-bonded region of TC4 titanium alloy was investigated. The results show that the diffusion-bonded region of TC4 titanium alloy has obvious dynamic softening characteristics at high temperature,and the flow stress decreases with the increase of deformation temperature and increases with the increase of deformation rate; The diffusion-bonded interface disappears after high temperature deformation,and the volume fraction of isoaxial α phase decreases with the increase of deformation temperature,accompanied by the emergence of short rod-like and plate-like secondary α phase, and the volume fraction of secondary α phase decreases with the increase of strain rate; When the deformation temperature reaches 1010 ℃,martensite α ""phase appears; Based on the hyperbolic sinusoidal modified Arrhenius equation,the hyperbolic sinusoidal constitutive equation and the thermal processing diagram of diffusion-bonded region of TC4 titanium alloy were established.The optimal deformation parameters of diffusion-bonded region of TC4 titanium alloy were determined as T=920~950 ℃, ε=0.01~ 0.1 s-1.