The "bond line" of the diffusion bonding interface is a common characteristic of the diffusion-bonded region in nickel-based superalloys. It significantly impacts the performance of the diffusion joint. Thermal deformation machining is an effective method to improve the microstructure and properties of a diffusion bonding interface. In this study, the thermal deformation behavior of the GH4169 alloy diffusion-bonded region was investigated at a deformation temperature of 1213~1333 K with a strain rate of 0.01~10 s-1 using a Gleeble 3800 thermal-mechanical simulation test machine. The results show that the "bond line" in the diffusion bonding region of GH4169 alloy can be effectively eliminated through thermal deformation. The evolution of the δ phase in the diffusion bonding interface region is affected by deformation conditions. When the deformation temperature is lower than the solution temperature of the δ phase, the residual spheroidized δ phase prevents the growth of recrystallization nucleation grains and affects the subsequent recrystallization process. The spheroidization degree of the δ phase can be enhanced by reducing the strain rate. When the deformation temperature exceeds the dissolution temperature of the δ phase, the dissolution of the δ phase creates an extra driving force for recrystallization, thereby significantly enhancing the extent of recrystallization. A hyperbolic sinusoidal Arrhenius constitutive equation, incorporating strain compensation, is used to describe the correlation between flow stress and deformation conditions in the diffusion-bonded region of the GH4169 alloy. The calculated values of the constitutive equation agree with the experimental values. According to the dynamic model of the GH4169 alloy diffusion bonded region, the optimal processing parameters have been determined. The deformation temperature is 1310~1333 K, and the strain rate is 0.01~0.05 s-1.