A promising technique to solve the microstructure degradation problem caused by conventional diffusion bonding process of copper (500–800℃) is low-temperature (400℃) diffusion bonding method. Shot peening treatment was applied to copper surfaces before bonding to active the diffusion of atoms under low bonding temperature. Four samples with shot peening time of 10s, 40s, 70s, 100s, respectively, were observed under optical microscope before bonding. Severe plastic deformation occurred, and fine-grained layer formed near the surface after shot peening. The thickness of the finegrained layer increased with the increase of the shot peening time. After low-temperature diffusion bonding, recrystallization was proved to take place. The tensile strength of the joint increased with the increase of the shot peening time. The highest strength was 314.5MPa with shot peening time of 100s, reaching 86.1% of the base metal.